A Neighbor With a Lot of Gall

Growing next to the sidewalk just around the corner is an eyecatching oddity. These should be leaflets of an ash tree's leaf, but instead they bear an uncanny resemblance to a butterfly's chrysalis.

This is a normal ash leaf, with a bunch of leaflets.

Here, the development of each leaflet has been altered to make the chrysalis-like structure. Sure looks like something should be living inside.

Open it up to find the midges living the good life, well protected by the distorted growth of the leaf, and with ample food to reach maturity in a month or so. The larvae drop to the ground, overwinter in the soil, then emerge in the spring as adults to climb up the ash tree in time to lay eggs in the emerging leaves. The midge injects the rapidly growing leaf with a hormone-like chemical that causes the leaf to grow in a conveniently distorted manner. (Nice description found here.)

The latin name for the midge, a kind of fly, is Dasineura tumidosae. Considerable internet searching yielded no common name other than "ash gall". Here's some more info.

One of the more common galls on ash is the ash flower gall, which can be seen in the canopy in the spring, before leaves emerge. Thinking back to our hike up Baldpate Mountain a month ago, I realized we had been looking up at an ash that looked like it had growths on the twigs high up, wondering what it was. Probably ash flower gall.

A question to be asked is how closely tied is the fate of all of these organisms to their host plant. If our ash species succumb over the next ten or so years to emerald ash borer, whose presence in New Jersey was documented for the first time this past week (more on this later), will all of these insect species find other hosts, or disappear along with the ash? A tree like the ash, which can develop considerable stature and grandeur, feeds an entourage of less charismatic creatures. At least one of them I can now count as a neighbor. 

Why the Native/Non-native Distinction Matters

Here are two examples of leaves being stripped by insects in the backyard. One example is likely harmless, and actually shows that there's a functional foodchain in this backyard habitat. The other signals the arrival of yet another severe blow to our local ecology.

Most people recognize jewelweed, the annual with tubular orange flower that feeds hummingbirds, and has a fleshy stem that some use to rub on poison ivy skin rash. The flowers hang like earrings, and turn into spring-loaded seedpods that are fun to put in the palm of the hand and explode. Used to seeing it grow robustly in low wet areas, I was surprised this morning to find one defoliated.

A few new leaves had sprouted from stems made bare by a caterpillar.

Closer inspection showed a busy caterpillar on the underside of new leaves. Some internet research (here and here) suggests there are several species of moth that feed upon it.

Though this one plant was defoliated, others in the garden are prospering. If the caterpillar is native, one can assume it's been consuming jewelweed for thousands of years, and so poses no threat to its favored plant species' survival.

Here is a much different situation--an arrowwood Viburnum showing signs of insect damage. Chances are good that this native Viburnum, which has flourished for a decade in our backyard, is not being eaten by a native insect with which it has coexisted for millenia. More likely the hungry caterpillar is the Viburnum Leaf Beetle. Imported from Europe, it has been spreading across the eastern U.S. Since it did not evolve here, the native Viburnums have had no chance to develop defenses to limit its consumption. As with the Emerald Ash Borer that is beginning to devastate our ash trees, the introduced Viburnum Leaf Beetle will likely cause radical changes, not only in our forests but in backyards as well.

Local nature, in effect, is sustaining one body blow after another, due to the introduction of non-native species, some of which unleash radical change. It's important to note how our world is being transformed by unintended acts while the news media focus on intentional acts of destruction. If a rogue arborist began randomly cutting down people's trees and shrubs, there'd be a great outcry and the destruction stopped. But if an accidentally introduced insect does the same, causing millions of dollars in damage, its accepted with a shrug and a sigh. Add the collateral damage known as climate change into the mix, and you see how profoundly vulnerable is our world, no matter how big the military or well trained the police force.

A useful approach to defining "native": 
There's a lot of confusion about what the word "native" means, and why it's an important distinction in ecology. Some contend that all plants and animals are native to the planet, and so all species should be welcomed everywhere with open arms. That supposedly openminded point of view requires denying the reality of co-evolution. It's really quite simple. When plants and animals evolve together for thousands of years, they adapt to each other's presence. A balance develops, in which plants evolve chemical or physical defenses that discourage animals from eating them into oblivion. Animals, in turn, develop the capacity to crack those defenses sufficiently to get the food they need to survive. There's a balance of consumption.

Here's a well-written column explaining how differently a plant like garlic mustard behaves where it evolved, vs. after being introduced to a new continent.

Searching for Monarchs in Princeton

The monarch butterfly, as most people know, is in trouble, due in part to a radical decimation of milkweed on more than one hundred million acres of farmland in the U.S. in recent years. Thus far this summer, I had seen a grand total of two monarchs, one having visited the raingarden in my front yard on Harrison Street. Another raingarden on Harrison Street, at the Spruce Circle senior housing, had just been bulldozed while in full flower.

With that traumatic step backwards in mind, I set out yesterday on my bike to check out a few spots elsewhere in Princeton. If a monarch were to travel around town at about the speed of a bike, wings warmed by the sun after a recent rain, would it find any prospective mates?

First stop was the meadow at the corner of Mountain Ave and the Great Road. The Joe-Pye-Weed was blooming as it does every year, but no monarchs to be seen.

Then a ride up the Great Road to Farmview Fields, where I had hooked the town up with Partners for Fish and Wildlife--a federal agency--to plant a meadow of warm-season native grasses in a stormwater detention basin that had previously been mowed as turf. More habitat, less mowing. Everyone was happy. I had added some native wildflowers, and others had seeded in. When I checked last year it was doing great. Yesterday, however, I was surprised to find the grasses stunted and the wildflowers gone. It hadn't been bulldozed, but something's wrong with the mowing regime, which should be just once a year during the dormant season.

Again, there's a sign that should signal that this is a special area, requiring a different management.

The heavy equipment had left some patches of ground scarred and bare. Mowing crews are so used to mowing these detention basins elsewhere that they may have started regularly mowing this one, out of habit. I had a job mowing a golf course one summer. It's not the kind of work that encourages thinking outside the box.

An unmowed area nearby showed what the basin should have looked like, with the "turkey feet" of big bluestem rising to the sky.

There was a swallowtail butterfly sampling the basin's meagre offerings, but still no monarchs.

Back down the Great Road to the opening in the fence, near Pretty Brook Rd, to take the boardwalk across the bottom of Coventry Farm over to Mountain Lakes. Lots of common milkweed in the field, but no signs of their being munched on by monarch caterpillars.

Finally, along the boardwalk near a big wet meadow of ironweed (the hydrologic conditions a raingarden imitates), I saw a lone monarch, flying about but not landing. As the monarch numbers have dwindled since the 1990's, the question arises, how do they find each other? They start each year in a small enclave in the mountains of Mexico, then spread out across vast areas of the U.S. and Canada. This migration, with one generation succeeding another as they move northward, is predicated on having sufficient numbers for individuals to find each other and mate. The lone monarch and the uneaten milkweeds offered little reason for optimism.

At Mountain Lakes House, a popular place for weddings and other gatherings, and also home base for Friends of Princeton Open Space, the raingarden I designed was prospering.

Lots of color there,

and in another rain garden in the driveway, but no monarchs to be seen.

There was still one spot to look, though, in the fields of Tusculum, preserved by Friends of Princeton Open Space and others, and packed with milkweed. To get there meant maneuvering through the now tattered evergreen forest of Community Park North. High winds in recent years have knocked down most of the pines and spruce, which really aren't natural to this area but had provided a deep forest feel that was enjoyable to walk through. Now, fallen trees have opened up the canopy, energizing an understory of invasive stiltgrass and honeysuckle.

Some trails are lined by young ash trees that will likely be attacked by the emerald ash borer when it reaches Princeton. This strangest of woods was not feeding optimism either.

The fields of Tusculum also looked different than in past years, perhaps again due to a mowing regime that might not be the best for wildlife habitat. Mountain mint, once a common wildflower there, was nowhere to be seen. And no monarchs.

But then, near Cherry Hill Road, next to a purple patch of tick trefoil and Indian grass,

monarchs, a pair, mating!

They flew over into the meadow to continue. Part naturalist, part voyeur, I lingered, wishing to document how long such pivotal acts take. It became clear that this was no brief rendezvous, so I moved on,

to the next field over, where common milkweed sprawled over more than an acre.  And there, another monarch, showing off its brilliant, speedy flight, ducking in and out among the milkweeds, as if in a hurry yet undecided as to where to land. It did land a few times, briefly, perhaps to lay an egg? I checked the undersides of leaves, but it was hard to tell from a distance where it had landed.

I biked home more hopeful than two hours prior. Those monarchs were starting the last generation of the year, the one that will fly all the way back to Mexico. On the way back, I passed the Princeton High School's detention basin just north of the performing arts center on Walnut Street. Now wouldn't that be a fine gesture, an act of generosity and belief in the future, if the school were to turn that empty, unused basin into a monarch meadow.

The "Second Forest" -- Fall Version

The second forest is a term I use to describe the understory layer of exotic invasive shrubs that populate most of our forests. It is essentially a second forest superimposed on the landscape, composed of non-native species that, being largely inedible to wildlife, do not support the local foodchain. You can see it this time of year, when the native species have lost their leaves but the exotic honeysuckle shrubs are still green. Note that the honeysuckle sticks to the higher ground in the distance. The second forest can be attractive, but ecologically it causes problems because the exotics not only stay green later into the fall but also green up early in the spring, shading out our native spring ephemeral wildflowers before they've had a chance to absorb enough solar energy to sustain them through to the next year. The photo is from Princeton's Mountain Lakes Preserve.

As the Emerald Ash Borer begins to kill off the many ash trees in our preserves, the canopy will develop many gaps, allowing more summer sunlight to reach the shrub understory. If that understory is largely exotic invasive species, then all that solar energy will go into generating foliage that is largely inedible to wildlife, and which produces berries of significantly less nutritional value than those of native species. The consequent reduction in functional acreage of open space is why it's so important to be taking action now to shift the understory from exotic to native species, so that our preserves can actually support diverse native plant and animal life.

I made this case as a member of the Princeton Open Space Advisory Committee this year. Hopefully, the committee's report will help town leaders see the strategic importance of habitat restoration, given the dramatic changes coming to Princeton's forests.

Invasive Plant Species in Princeton

This Monday, May 22 at 7pm, the Princeton Public Library will host a presentation on invasive species in Princeton by Mike van Clef, of the NJ Invasive Species Strike Team. There will also be representatives of FOPOS and DR Greenway participating. Princeton municipality hired Mike to develop a report on invasive species in Princeton preserves, and in 2016 he and two interns worked through the summer on invasive species control. Because of the massiveness of the problem, they focused on emerging species--those whose populations are still small enough that a summer's worth of control would make a difference. 

We may look back on 2016 as a pivotal year, when the town began investing in invasive species management, much as 2000 marked the beginning of professional deer management in town. 

Although it may sound self-congratulatory, another important date in Princeton's history of invasive species management would be 2006, when the Friends of Princeton Open Space hired me as their first Natural Resources Manager. 

When I arrived in town in 2003 on the coattails of my wife's appointment to the Princeton University faculty, a couple things quickly became obvious. First, Princeton had done wonderful work preserving land for open space. Second, the open space itself needed a lot of work. Though the trees in Princeton's woodlands were mostly native, the understory vegetation was often dominated by nonnative, invasive plants. Stiltgrass, honeysuckle and privet, to name but a few, had filled the void created long ago when the diverse native understory had been plowed under, back in Princeton's agricultural era. In the decades since, the native trees had rebounded, but the understory had either not come back, or succumbed to heavy browsing pressure from deer.

Because wildlife tend not to eat the leaves of nonnative plants, their proliferation in preserves renders the habitat largely inedible. Yes, birds can eat the berries of nonnative shrubs like honeysuckle, but if the insects and other wildlife aren't eating the leaves, then much less of the solar energy captured in the plants can move up the food chain. 

I proceeded to make the case that Princeton could expand its effective acreage of open space through management for native species. As most readers know, I've been leading workdays and nature walks ever since, for six years as an employee of FOPOS, and more recently as president of the Friends of Herrontown Woods (FOHW). Highly motivated volunteers like Tim Patrick-Miller and Andrew Thornton, and more recently Kurt and Sally Tazelaar at Herrontown Woods, have had a positive impact over time. Meanwhile, FOPOS has sustained its Natural Resources Manager position--having just hired the fourth to hold that position--and continues to do invasive species removal at Mountain Lakes Preserve. After so many years of nonprofit, largely volunteer efforts, to finally get municipal support through Mike's crew this past summer was a real boost that we hope will continue.  

It's important to note that Mike van Clef's study of invasive species in Princeton is limited to parks and preserves owned or managed by the town. There are large expanses of open space owned by the state (Princeton Battlefield and DR Canal) and by the Institute for Advanced Study (the 600 acre Institute Woods). Portions of the Battlefield and the DR Canal are being overrun by porcelainberry (in photo), which barely registers in Mike's survey, and mile-a-minute vine is beginning to show up there as well. I've been trying to help fill a void in management, co-leading workdays at the Battlefield and, in the proactive "early detection, rapid response" tradition, dealing with two small infestations of Mile-a-Minute in town before they become unmanageable. Another nonnative plant that's spreading rapidly, both in people's yards and in nature preserves, is lesser celandine (a.k.a. fig buttercup). It can only be controlled in the spring, long before summer interns begin work. Ideally, a town-wide coordination to manage invasive species would be developed.

The town's investment in invasive species control comes at a critical time. With the emerald ash borer (another highly invasive introduced species) poised to decimate Princeton's most numerous native tree, large gaps will be created in our forest canopy, allowing light to penetrate to the understory. Princeton's long investment in deer culling has allowed native shrubs like spicebush to make a comeback, but in many woodlands, the understory is dominated by nonnative shrubs and stiltgrass. Wildlife have evolved over millenia to eat native species. It's a question of whether edible natives will capture that extra sunlight in the understory, or the privet, winged euonymus, honeysuckle, barberry and Photinia. The foodchain depends on our intervention.

The primary argument for habitat management remains that, by improving the quality of habitat, Princeton effectively increases the functional acreage of open space. This is true not only for wildlife but also for people. Controlling invasive species also makes the human experience in preserves more rewarding. As we've cut down invasive shrubs at Herrontown Woods, we've not only made more sunlight, water and nutrients available for native species to prosper, but also have opened up pleasing vistas and made the woods more navigable. 

The problem of invasive plants may seem overwhelming, but we can take our inspiration from the deer, who transform landscapes through the cumulative impact of browsing here, there, and everywhere, one mouthful at a time. The pioneers, too, thought the continent too vast to ever tame. Though their goal wasn't exactly to increase native plant diversity, they showed how steady effort makes a difference over time. Ideally, professionals will complement existing volunteer efforts, and the locals who know the preserves best will help steer the professionals' interventions. 


At Monday's presentation, there will also be discussion of a list of invasive species that people are being discouraged from planting. It's a very long list, and I wish it could better reflect the broad spectrum of invasive behavior we see in the field. One reason the list is so long is that, though many of the species on the list may not be found spreading into Princeton's nature preserves, history shows that invasive behavior in nonnative species may not become manifest until many decades after they've been introduced. Chinese silver grass (Miscanthus sinensis) is a case in point. Though it has yet to spread to Princeton's Tusculum meadows, it is now posing a big problem for meadows at Duke Farms up in Hillsborough. The flyer for the library event includes a photo of butterfly bush, which I've never observed exhibiting invasive behavior. Monday's presentation may help put local observations in a broader context.

Update: Full house for the program! Good to see.

Native Chestnuts in Princeton--the Next Generation

Many of us have lived our whole lives without seeing a mature native American chestnut tree. An excellent NY Times Magazine article described it as a true gift of nature, the perfect tree, growing straight and tall, with rot-resistant wood, and bearing nuts that were easily gathered and eaten, sustaining wildlife and people alike. My first encounter with the American chestnut was the sight of their fallen trunks in a Massachusetts forest, 70 years after the fungus that causes chestnut blight was discovered in NY city in 1904. The massive trunks I saw, lying on a slope in the shade of young white pine, were among the billions that the accidentally imported fungus would ultimately kill in the U.S. Since the roots survive the fungus, there was still a living community of underground chestnut trees beneath our feet in that Massachusetts forest. One of the roots had sent up a sprout about twenty feet tall--promising, one would like to think, but its slim trunk was already ringed by the fungus, its fate sealed before it could bear nuts. 

One of the projects I'm involved in is reintroducing native chestnuts to Princeton. The initiative began in 2009 with an email from Bill Sachs, a Princetonian with considerable expertise when it comes to nut-bearing trees. Bill reported that Sandra Anagnostakis, "one of (if not the) world’s leading experts on the pathology of American chestnut," had agreed to supply us with disease-resistant, hybrid American chestnut trees. Sandra's efforts to breed resistant native chestnuts at the Connecticut Agricultural Experiment Station over many decades was apparently unconnected to the American Chestnut Foundation. The trees were 15/16th native, and Bill with occasional help from me and others proceeded to plant them at the Princeton Battlefield, Harrison Street Park, the Textile Research Institute, Mountain Lakes and Herrontown Woods. 

Some fared better than others. Many, despite having been bred for resistance, nonetheless struggled with the blight that had laid the mighty tree low a century ago. This fall, however, paralleling our work to bring back native butternuts, one of the chestnut trees has borne fertile seeds.  

Bill made repeat visits to the tree to collect the nuts as they ripened. The deer likely got many, but he managed to gather quite a few, some of which he encouraged me to cold stratify. Stratification has always been an intimidating concept for me, suggesting sophisticated manipulation to get a seed to germinate, but in this case it turned out to be not much more than stuffing some seeds in a bag of moist peat moss and leaving it in the back of the refrigerator for awhile. 

The tree, hosted by TRI near Carnegie Lake in eastern Princeton, bore generously despite significant pruning by the periodical cicadas early in the growing season. 

This past summer a friend had sent me a photo of another chestnut tree that, being smaller, was much more affected by the cicadas' egg-laying activities. They cut into stems to lay their eggs, which ends up killing the foot or two of stem beyond where the eggs are deposited. 

We'll see how these various trees do over time, and if a second generation of these mostly native chestnuts comes into being. The NY Times article was mostly about efforts to develop a blight-resistant American chestnut through genetic modification. That thirty year project, with a geneticist named William Powell as the main protagonist, has been successful. They managed to find a gene in wheat that confers resistance when inserted into the chestnut's genome. 

Adding one gene would seem a much more precise and less intrusive means of correcting a century old wrong than adding many genes, most of which are irrelevant to improving resistance, from asian chestnuts. But don't expect these ever so slightly and efficiently modified native chestnuts to be available any time soon. There are strict regulatory hurdles that must be overcome. 

For me, the situation demonstrates two powerful forces in the human world. One is the fear of the slippery slope. Would an elegant genetic fix for the American chestnut open the doors to a wave of less admirable genetic modifications of our world? The other powerful force is our focus on regulating intentional change, while allowing unintentional change to run rampant. While the government spends years deliberating over one gene being added to the native chestnut tree, global trade is introducing an ongoing wave of new organisms to the country, any one of which could be the next emerald ash borer or spotted lanternfly. 

In the meantime, we'll be thankful for the mostly native chestnuts we have, and see what we can grow.

Below is more info I've taken from some of Bill Sachs' emails. Click on Read More. 

Murder Hornets and Princeton's Cicada Killer

The scary reports about murder hornets offer an opportunity to write about invasive species and insects generally. "Murder hornet" is a nickname, but the insect's real name, Asian giant hornet, is not very reassuring. There have been some scary videos making the rounds. The NY Times article was less sensationalistic, and captured well the potential threat along with the actions being taken to counter it. Rutgers hastened to clarify that the insect isn't found in the northeastern U.S.. And it's still not clear whether the AGH (Asian giant hornet) has established a population in the northwest, and if so whether the population is still small enough to be eradicated.

Big insects are scary. One nightmare remembered from childhood was of an ant about two feet long. I had a memorable bike ride home one day with a wasp having perched on my shoulder. I decided to just let it sit there, and eventually it flew off. The more I learn, though, the less scary most insects become. Late last summer, I waded out into a lawn full of blue-winged wasps flying about, knowing they were harmless. Knowledge can lead to a gentle response to something seemingly dangerous in nature. When the fishhook-shaped thorn of a multiflora rose bush pricks the skin, the best thing to do is relax, move towards the shrub rather than away, calmly cut the stem to which the thorn is attached, or rotate so the thorn has a chance to slip back out of your clothing.

Learning more about the Asian giant hornet can bring at least a little reassurance. Along with the uncertainty of its establishment in the U.S., I heard via an invasives listserve that "AGH does not attack people unless it feels threatened", and though they do pose a threat to honey bees, they only "attack and kill other bees in the late summer when developing males and future queens need extra protein to complete their life cycle."

The largest wasp in the Princeton area is the cicada killer, which looks much scarier than it actually is. Like dragonflies, they can tackle insects in midair. Ten years ago, there was a colony of cicada killers living near the Princeton Community Pool. Cicada killers are large wasps in Princeton that dive-bomb cicadas in mid-flight, then haul them back to their underground nests to use as food for their young. They pose little danger, but the colony was exterminated by the parks department because the wasps alarmed people walking by in their bathing suits. (Photo is a dramatization featuring our local cicada killer and an unknown actor.)

While pointing out that some threatening looking insects can be benign, I've also long advocated for action on invasive species. As introduced plants like lesser celandine and porcelainberry spread their smothering growth across Princeton's open space and lawns, there is an opportunity to keep them out of some areas through proactive action. It's been very hard to get people to think strategically, however.

The Asian giant hornet is at least being taken seriously. Quick action could prevent it from getting established in the northwestern U.S., though usually an introduced species is already established by the time anyone sees it in the wild.

As with COVID-19, there are questions as to how the hornet would adapt to climate in the U.S. The L.A. Times questioned whether the AGH would adapt to California's cool summers and warm winters.

Some introduced insects become enduring pests, like Asian tiger mosquitoes that bite annoyingly during the daytime, and the Emerald ash borer that has decimated ash trees. On the other hand, we hear little about the killer bees that were touted as such a big threat in the 1980s. The best news would be that the Asian giant hornet hasn't become established after all.

ALERT: Viburnum Leaf Beetle Spotted in Princeton

During an otherwise very positive weeding session in Harrison Street Park, I spotted a small Viburnum shrub that appeared to be a ghost of its former self. Every last leaf had been skeletonized. As I took a closer look, I was afraid of what I might find. Native to Europe, the Viburnum Leaf Beetle was transported to our continent and has been spreading across the eastern U.S., decimating native and exotic Viburnums as it goes.

This closeup corresponds with what can be found on the web. As far as I know, and I'll check with the extension service, this is the first documented occurrence in Mercer County. (Update, May 20: I called today, and they are in the process of confirming a sighting in Pennington.) The map on the NJ Invasive Species Strike Team website shows documented occurrences in other areas of NJ. My first encounter with it was some five years ago in a park in Pittsburgh, where a grove of arrowwood Viburnums (V. dentatum) had been transformed by the insect from robust green to brown ooze.

The only good news is that only two Viburnum shrubs in Harrison Street Park had been visually affected. This photo shows the early stages of attack. I tried to kill every last larva I could find.

Chances are, this is not the only infestation in Princeton. Homeowners should check any Viburnums in their yards for signs of damage. Some suggestions for control can be found at this link. Not all Viburnums are equally vulnerable, as this Cornell University list shows. Among our three most common native species, arrowwood Viburnum (V. dentatum) is the most vulnerable, followed by mapleleaf Viburnum (V. acerifolium), with blackhaw Viburnum (V. prunifolium) being the most resistant. Arrowwood Viburnum is generally found in low-lying woodlands. Mapleleaf Viburnum is a small shrub, rarely encountered except along the ridge. The blackhaw Viburnum is the largest and most common native Viburnum in Princeton. A Penn State website suggests that the insect prefers Viburnum species with less pubescence on the leaves.

Most people have heard of Emerald Ash Borer by now, which was spotted for the first time in Mercer County last year. One ecological consequence of losing most of our ash trees over the next ten years is that more sunlight will then reach the understory, which is dominated by non-native shrubs like honeysuckle, privet, asian Photinia and winged Euonymus. Viburnums are a main component of the native understory. If they are severely weakened by Viburnum leaf beetle, then they'll be even less able to compete with exotics for that additional sunlight. A recent presentation by entomologist Douglas Tallamy in Princeton offered evidence that not only is the foliage of native plant species necessary for the survival of countless species of insects, but their berries are much more nutritious for birds. How we are to keep foodchains intact in our forests is something of a question.

In addition to being vigilant and acting quickly if an infestation is found, one thing to do is take a moment to appreciate the Viburnums and ashes we have--the play of light on their leaves, the colors they turn in fall. In a largely unregulated world where powerful forces of change continue to be unleashed, there's a heightened poignancy in what we all too often take for granted.

Going Negative On Natives

There's a movement afoot to blur the distinction between native and non-native species, and to berate, belittle, besmear, besmirch, and otherwise ascribe questionable motives to those of us who seek to restore native diversity. The arguments and accusations put forth are highly flawed, including a recent oped in the New York Times. Below is a rebuttal I originally posted two weeks ago at newscompanion.com. This issue is coming up more frequently, including an NPR Science Friday show today, which I haven't listened to as yet.

The New York Times is one of the bedrocks of news, which makes it hard to understand why its opinion page would show a weakness for ill-informed attacks on native plants and their proponents. The latest is by Verlyn Klinkenborg, a point-by-point rebuttal of which can be found further down in this post, but his is just one in a series.

First in my memory is George Ball, president of Burpee Seed Company and former president of the American Horticultural Society, who despite these distinguished labels launched an error-filled broadside (Border War, 3/19/06) against people who promote the planting of native flora. In his words, people who promote natives are xenophobic, narrowminded, the horticultural equivalent of radical fundamentalists, utopian, elitist snobs, anti-exotic partisans, and (last but not least) dangerous to a free society.

Then there was Sean Wilsey, (High Line, Low Aims, 7/9/08) who spoke disparagingly of the proposal to plant a ribbon of native species on Manhattan's High Line. Apparently lacking any botanical or ecological knowledge that might have heightened his appreciation of the plan, he made it sound like the High Line would be little more than a linear patch of weedy sumac--a species he may have confused with the ubiquitous non-native Tree of Heaven. Time, and the spectacular congregation of native plants that now thrive on the very popular elevated walkway, have proven him wrong.

The latest installment of this attack on native plant advocacy, as mentioned, arrived this past week (Hey, You Calling Me an Invasive Species?, 9/7/13), written by a member of the Times' editorial board, Verlyn Klinkenborg. Avoiding George Ball's name-calling and Sean Wilsey's dismissive tone, his thesis is that the distinction between native and nonnative species is now an arbitrary one, given the passage of centuries and the ever-expanding influence of humans on the natural world.

Klinkenborg's opinion piece was prompted by recent public protests against a plan to thin out a dense forest of non-native eucalyptus trees growing on Mount Sutro in San Francisco. The University of California San Francisco (UCSF) owns the property, which the local fire department has said is in urgent need of thinning in order to protect nearby buildings from the highly combustible eucalyptus. Reducing the dense shade will improve the health of the trees while providing some light for native vegetation to grow beneath them. Sounds benign, yet locals who walk in the forest are calling the proponents of the plan "plant facists" who want to impose the tyranny of nativism on a woods that is perfect just the way it is.

Joining the chorus of protest, Nathan Winograd, an animal rights advocate who blogs on the Huffington Post wrote a post about the Mount Sutro tree-thinning plan entitled "Biological Xenophobia: The Environmental Movement's War on Nature". Adopting the strident tone of George Ball, he has nothing but contempt for the concept of native plants, preferring that "every life that appears on this Earth is welcomed and respected." Apparently, he's never grown any plant he valued enough to save from the weeds.

The most informative report, as opposed to opinion, on the San Francisco controversy that I could find is here. The university describes the plan this way: "Under the guidance of an outside licensed arborist, UCSF will remove approximately 1,250 trees, each less than 6 inches in diameter, while also thinning shrubs and mowing non-woody perennial plants in the 100-foot buffer zone. All told, the work will encompass approximately 15.6 acres of the 61-acre Reserve."

Here is a point by point rebuttal of Mr. Klinkenborg's opinion piece:

"Since the 1880s, there have been blue gum eucalyptus trees growing on San Francisco’s Mount Sutro, which lies just south of Golden Gate Park. Recently, the University of California, San Francisco, which owns most of Mount Sutro, has been trying to thin the dense eucalyptus forest. The reason is fire control — eucalyptus trees are “fire intensive,” shedding a lot of debris and burning with unusual volatility. But the effort to cull the Mount Sutro forest has been met with strident protest by residents who want to see the eucalyptus left untouched."

Mr. Klinkenborg only mentions fire once in the oped, but fire hazard is a big deal in the California landscape, and the planting of Eucalyptus trees close to structures has doomed many a building when the trees' high flammability causes them to explode. The link he offers, another opinion piece in a distinguished scientific journal, Science, actually offers compelling reasons to alter the forest. There's the current fire hazard to reduce, and the opportunity to improve habitat for the resident great horned owls by re-establishing some native flora. 

By the standard of the California Native Plant Society, eucalyptus, which were brought from Australia, are officially nonnative trees because they were introduced after the first European contact with the New World. But the trees on Mount Sutro have been there within the memory of every living San Franciscan, and to the generations who have grown up within view of them, it seems almost perverse to insist that they are aliens.

No science here, just an anthropocentric view that wishes the rest of nature to conform to the human sense of time.

To keep a clear distinction between native and nonnative species requires nearly geologic memory. 

No, one hundred and thirty years, or even three or four hundred, is not even close to a geologic scale.

But humans, like most species, don’t live in the past, where the distinction originates. In the present, the difference is largely immaterial. 

This isn't true. Though wildlife don't literally live in the past, their tastebuds do. Herbivores tend to be extremely conservative in their food preferences. Whether it be deer or the larvae of moths and butterflies, they continue to reject exotic species introduced hundreds of years ago. They still prefer to eat the native species, which gives exotics a competitive advantage, which makes native plants rare, which then limits wildlife's food options. 

Native or nonnative, California’s eucalyptus trees, like the starlings of Central Park, have come to seem original just because they predate us.

Again, he imposes an anthropocentric view on nature.

Of course, the vast majority of nonnative species have not been intentionally introduced, as the Mount Sutro eucalyptus were, but have been distributed accidentally, unnoticed baggage in the wanderings of our species.

Whether a species is introduced intentionally or unintentionally has no bearing on the potential harm the species can do, just as the impact of human-caused global warming will bear no relation to whether we have intended to change the climate or not. 

Some species — invasive ones like kudzu, Japanese knotweed, rabbits and rats — find almost unlimited room for expansion in their new environs, often overwhelming native species. But not all introduced species are invasive, and pose a threat only when they outcompete native species.

Excellent! It's so important to make the distinction between invasive and non-invasive species. 

It’s important to remember that the distinction between native and nonnative depends on an imaginary snapshot of this continent taken just before European contact. 

Not so imaginary, really. Though American Indians transformed the landscape, spreading some plant species along trade routes, favoring some species through cultivation or burning, or denuding the landscape, e.g. around Teotihuacan to heat the plaster for their pyramids, the massive influx of species from other continents did not begin until Western colonization. It's well known which species are or were part of a particular plant community. The bur oak savannas of the midwest, which had disappeared due to the invasion of buckthorn and other exotics, were pieced back together through research and restoration, and now flourish once again. Whole books describe in detail the various plant communities of a given region, such as this onedetailing the plant communities of North Carolina. 

               That distinction is becoming even harder to make as climate change alters the natural world.

A new study from the University of Exeter and Oxford University finds that plant pests and diseases have been migrating northward and southward an average of two miles a year since 1960. This suggests that the plants on which they prey have been moving at similar rates. In places like the Adirondacks, for instance, you can follow the boundary between southern and northern tree species as it shifts northward, year by year. As plants and their pests adjust their range, under the influence of global warming, what becomes of the distinction between native and nonnative? 

Plants and animals have been shifting their regional boundaries throughout the last four hundred thousand years, as glaciers advanced and receded. Human-caused climate change is happening much more rapidly, which is one reason why it is proving so destructive, but most plant species have broad geographic ranges. Climate change doesn't mean that plant communities developed over millenia suddenly have no integrity. 

To any individual species, it doesn’t matter whether it’s native or not. The only thing that matters is whether its habitat is suitable.

 Again, because herbivore food preferences tend to remain unchanged hundreds of years after the introduction of exotic species, suitable habitat tends to equate with native plant species. 

And this is where we come in.
For the most part, we don’t have an immediate impact on the species that surround us. But we do have an immediate impact on their habitat, which determines whether they survive or, in some cases, shift their ground.
Nearly every habitat on this planet has been affected by humans, no matter how remote it is. In the past decade, for instance, the habitats of grizzly bears high in the Rocky Mountains — places most of us never get a chance to visit — have been significantly altered by global warming. As the climate warms, the mountain pine beetle has managed to winter over and destroy vast tracts of whitebark pine trees, which produce pine nuts that bears eat.

When I visited a hillside in Smokey Mountain National Park where hemlock had been wiped out by the exotic wooly adelgid, growing beneath the dead trunks was a riot of native wildflowers and brambles, representing a plant community that deep shade had suppressed. The devastation of whitebark pine trees in the Rockies is tragic, and the loss of that important species may have broad ramifications over time for that ecosystem, but that doesn't mean that native landscapes suddenly lose all meaning and relevance because one species drops out.

CONSIDERED in this light, the natural world as a whole begins to look like Central Park — an ecosystem where human influence is all pervasive. Parts of the park seem almost wild, but every creature in Central Park, native or not, has adapted to a world that is closely bounded by human activity. It is nature bordered by high-rises, intersected by paths and roadways, basking under artificial light at night.

In late August, a group of scientists and students from the City University of New York’s Macaulay Honors College spent the day cataloging all the nondomesticated life forms living in the park. It will take a while to compile and compare the data, but even the anecdotal reports from that single day show how diverse and surprising the park’s ecosystem can be. It isn’t all squirrels and pigeons. The group reported sightings of several unexpected species — a diamondback terrapin in Turtle Pond, a Wilson’s warbler in the North Woods, a bullhead catfish in the Harlem Meer. And though it might seem like a stretch to talk about ecosystems in Central Park, that is exactly what the group found — a healthy mix of species, overlapping generations within many species, and a sense of balance, especially within the aquatic zones.

Actually, a lot of work has been done to restore native species and habitat in Central Park, and it's the only sizable green space for miles for wildlife like birds and insects to gravitate to, so it's not surprising it would exhibit some diversity.

Nature in Central Park can’t be neatly divided into native of nonnative species, and neither can it be on Mount Sutro. The eucalyptus trees that grow there may be naturalized rather than native, but try telling that to all the other creatures that live in those woods or the people who hike there.

 This would be more convincing if it actually described what diversity resides on Mount Sutro. In Princeton, we had a woods that was densely planted in the 1960s with white pine and spruce--species whose native range lies farther north. The woods had considerable charm and a nice mood to it, but it was an ecological desert, with little more than garlic mustard growing in the deep shade and thick mulch of the evergreens, and reportedly an owl or two making use of the dense canopy for protection. (Mount Sutro, from what descriptions I could find, looks to be similarly slim on diversity, dominated by the eucalyptus, with an understory of English ivy and poison ivy, and a stifling and highly flammable thick mulch of eucalyptus litter.) 

Their trunks weak from age and crowding, most of the pines and spruce in the planted woods in Princeton fell during several ice and wind storms, leaving an impenetrable mess that will become a fire trap as the debris dries out. Ash trees, the only seedlings that the too-numerous deer didn't eat, are now taking over, and before long, the introduced Emerald Ash Borer will arrive to kill all the ash.  

A similar fate could await the planted woods on Mount Sutro, in the form of a cataclysmic fire. That, though far more destructive than what the university is trying to do, would not be as controversial, because it would occur due to inaction rather than action. I'm well aware of the capacity for good intentions to go awry, but sometimes inaction can be the most destructive action of all.

And when it comes to the distinction between native and nonnative, we always leave one species out: call us what you will — native, naturalized, alien or invasive.

I don't want to read too much into this, but Mr. Klinkenborg seems to be suggesting here that because we are a species that invaded the American continent, we therefore cannot be judging other invasive species. With such logic, our compromised position brings into question our capacity to understand nature and act upon what we know. 

The attempt to blur the distinction between native and non-native depends on a highly simplified view of nature and evolution. It ignores the deep interconnections species develop while co-evolving over thousands of years.  It sees no symbiotic relationship between soil fungi and plant roots, between an insect and its obligate host plant, between a particular species of ant and the plant that depends upon it to disperse its seeds. Some species, like humans, are highly adaptable to new circumstances. Others are not. Embracing non-native landscapes may give people the comforting illusion of being open-minded, but it closes the door on those more conservative, less adaptable species. 

Related Writings by Verlyn Klinkenborg

It's long been my observation that environmental issues get marginalized on the opinion pages of the news media, likely because columnists and editors tend to lack training in the life sciences. If environmental issues come up, they tend to be treated in isolation rather than seen in the broader context of economics and political concerns. On the New York Times editorial board, Mr. Klinkenborg appears to represent the sum total of biological expertise. His doctoral degree from Princeton University is in english literature. I'm all for self-education, and hopefully he took some biology-related courses along the way. 

Some of his writings for National Geographic appear to contradict his opinion piece dismissing the relevance of native habitats. For instance, an essay on the Endangered Species Act states that people

"discovered, too late, how finely attuned to its home in the cordgrass the dusky seaside sparrow really was. That last bottled sparrow is what a species looks like when its habitat has vanished for good."

In an essay on the tallgrass prairie, rather than downplaying the importance of native plant communities, he seeks a deeper understanding of them:

"The hard part here in the Flint Hills—and in any of the few remaining patches of native prairie—is learning to see the tallgrass ecosystem for itself. It is a study in the power of modesty."

Rather than giving simplified plantings like the eucalyptus on Mount Sutro equal status with native plant communities, he states:

"In most of America, agriculture has meant replacing the incredible complexity of a natural ecosystem with the incredible simplicity of a single crop growing on bare ground."

That incredibly complex prairie ecosystem, however, is threatened by an invasive non-native plant called Sericea lespedeza (Korean bushclover). Rather than showing concern about the impact of that invasion, Mr. Klinkenborg worries about the human intervention to counter the invasion:

"There is also a worrying trend toward ground and aerial spraying to control a highly invasive weed called sericea lespedeza, introduced decades ago to curb erosion around mines and provide forage and cover for wildlife around reservoirs."

Now, I happen to know Sericea lespedeza well. I've seen how it moves in and eventually replaces a richly diverse native meadow with a monoculture. Though originally touted as a good wildlife food, both its seeds and foliage provide little nourishment. Its roots release toxins that discourage other plant species. If you're looking for an example of intolerance, of a refusal to "play well with others", Sericea lespedeza is Exhibit A. When it invades new territory, land managers have a choice--either let the noxious weed continue to degrade native habitat, or attempt to limit the weed's destructive impact by intervening, often with selective herbicides.

The objections of Klinkenborg and others to intervention are in part a failure to make distinctions. They want to blur the distinction between native and non-native species. The toxicity of herbicides varies according to type and method of application, but its easier for protesters to demonize them all. Nathan Winograd, in his broadside against native plant advocates, wishes to obliterate all distinctions and treasure every living thing equally. More broadly in national discourse, we see a trend towards accepting all opinions as worthy, whether they are founded on fact or fancy.

Saying that we don't need to make these distinctions, nor intervene to restore native plant communities, sounds less to me like open mindedness than a convenient way of letting ourselves off the hook.

Mile-a-Minute Found at Princeton Battlefield

As if the massive invasion of porcelainberry, the "Kudzu of the North", at the Princeton Battlefield were not enough, I just discovered a patch of Mile-a-Minute there. This is, fortunately, only my second sighting of the prickly, fast-growing invasive in Princeton. The first sighting was in August of 2007, when I spotted it in a flower bed across Harrison Street from the Princeton Shopping Center.

For that first patch, it was relatively easy to contact the owner and convince her that it needed to be removed. The patch at the Battlefield is somewhat larger, about ten feet square, and has already produced berries that could be transported by birds to other locations. The next step is to go back with a sturdy pair of leather gloves and trash bags, and remove every last bit.

That Mile-a-Minute has a small foothold at the Battlefield suggests that it could have popped up most anywhere else in Princeton, so keep an eye out. The plant is an annual with distinct triangular leaves and a prickly stem reminiscent of our native tear-thumb. It should be pulled out and, if it has berries, placed in a garbage bag and put out for the trash. DO NOT put it in the compost, because the berries could then be spread.

It should be noted just how vulnerable we are to invasions of this sort. The Emerald Ash Borer's arrival in Princeton is a prime example. Accidentally imported to southeastern Michigan twenty years ago, it became established and therefore impossible to eradicate, because there was no "early detection, rapid response". Maintenance of the Battlefield grounds consists of mowing. Anything in the plant world beyond lawn requiring intervention is thus left to the chance interest and commitment of volunteers without a budget.

I happened to notice the Mile-a-Minute vine while checking the status of the ornamental flowering dogwoods planted long ago along the edges of the northern field at the Battlefield. I've been cutting the vines off, most years, but the porcelainberry is becoming increasingly dominant, smothering many of the dogwoods and other trees along the field's edge.

Here's a dramatic example, a dogwood barely visible beneath an oppressive cloak of porcelainberry.

On a planetary level, climate change was detected, but many with power to act have lacked a basic understanding of the consequences of delay. Here's where a naturalist's experience with invasives, or even a backyard gardener's experience with weeds like stiltgrass, mock strawberry, or ground ivy, can give insight into the importance of quick response. A ten foot patch of Mile-a-Minute seems minor, but without action, its berries will spread and the problem will quickly become too intimidating to dare act against. Bureaucracies do this all the time, as with Burmese pythons in the Everglades. Early warnings are ignored, and the problem doesn't become officially recognized as a problem until it's too big to solve.

Meanwhile, the vast lawn continues to be mowed, offering a superficial reassurance to passersby that the landscape is under control.

Recreational Trails and Resilience

The Friends of Herrontown Woods and other stewards of natural lands in Princeton have been asked to give input to the state bike/ped office and the Federal Highway Administration about trail resilience in these times of rapid change. I decided to put my feedback into a blog post. We steward trails at Herrontown Woods and Autumn Hill Reservation in Princeton, NJ--about 220 acres total. Fit into the categories we were asked to address, here is some of what we've learned over time:

Trail vulnerability and resilience to natural hazards

Climate change is impacting our trails in multiple ways. Trees still pull water out of the soil during the growing season, making most trails reasonably dry during the summer and fall. In the past, winters were cold enough to freeze the ground in the winter. Now, with warmer winters, trails can get wet from rains in the fall and remain wet and muddy until the trees awaken again in late spring. 

Trails are becoming more vulnerable to erosion, give the more intense, longer, and more frequent rains, and the reduction in freezing in winter. Trails on a slope can become like streams as they catch runoff from the surrounding ground and convey it downhill. This makes water bars, which serve to divert runoff from trails, all the more important to build and maintain. 

As ash trees killed by the introduced Emerald ash borer become brittle over time, they will fit in the category of natural hazards. We've been fortunate to be able to take some down in the vicinity of our botanical garden, but it would be impossible to cut down all of them in the forest. They can serve as useful snags for wildlife, at least.

Designing trails for climate change and future conditions

We ground-truth potential new trail routes during the wettest times of the year. This has become all the more important as weather becomes more extreme. It's the only way we can know whether a particular route will be usable year-round. A route that looks dry during the summer may be impassable in the spring, when vegetation has yet to pull moisture out of the soil. This is the problem with having trail consultants spend a couple days in a preserve, and then make recommendations about trail routes. Ongoing observation is really helpful.

In some of our soils, it is the roots that maintain the firmness of the soil. We've been deceived at times by a seemingly dry route that, when it becomes a trail with lots of foot traffic, becomes muddy due to the breakdown of the underlying root structure that had been holding the soil together. 

No trail can be perfectly designed. We fortunately have a source of local "native" stepping stones that we can lay down on particularly muddy patches, and we use some boardwalking. Over time, we hope this will keep trails passable even as rain increases. 

Trails providing ecosystem services

Trails provide access to areas to cut invasive species or do other stewardship work. If invasive species are controlled along trails, the trails become essentially a corridor of restored habitat. Interestingly, trails can sometimes provide the necessary combination of disturbance and additional light necessary for some wildflower to grow that would otherwise get smothered by leaves or shade in off-trail areas.  

On the downside, trails can intrude on habitat, and also provide a route by which invasive plants like stiltgrass can penetrate into otherwise uninvaded areas of the preserve. 

Use of trails during emergencies (evacuation routes, emergency vehicle access, fire suppression, etc.)

We invited the the local rescue squad to do a practice rescue in our preserve. It was very helpful in acquainting them with the lay of the land. We also showed them areas where accidents could potentially happen, and are working on a better map of the preserve showing access points. 

Trails can serve as potential fire breaks, whether for fire suppression or for prescribed burns. We have yet to use fire as an ecological tool in the preserve, but fire often has a positive and historically important role in open spaces if prescribed and carried out appropriately.

Use of recreational trails during public health emergencies

We've seen a dramatic increase in trail use this past year, as well as an increase in volunteers to help at our preserve. Though hikers tend to be conscientious about wearing masks, some will want to avoid encounters along narrow trails. That gets us looking at how we could provide at least one trail that is wider than others. 

Nature has served as an indispensable balm, refuge, and recreational outlet for people during the pandemic. The pandemic has made nature preserves ideal for those who love not only plants and wildlife, but socializing safely with people as well. 

A New Environmental Resource Inventory for Princeton Takes Shape

There's a nice writeup on Princeton's Open Space Manager, Cindy Taylor, in TapInto Princeton. She'll be leading a presentation on Wednesday, Feb. 22, about the new edition of the Environmental Resource Inventory (ERI) that she's been working to prepare for Princeton. Among the many others contributing to the update are councilwoman Eve Niedergang and members of the Princeton Environmental Commission (PEC). The PEC will host the presentation, which should get going soon after 7pm. The public is encouraged to tune in and participate.

If you are wondering what an Environmental Resource Inventory is, you can take a look at the current ERI, which I played a considerable role in creating. Starting in 2007, as a member of the PEC, I worked closely with a consultant, Chris Linn, on that previous update of the ERI, the first update since 1978. 

It seemed appropriate that a resource inventory would include plant inventories--long lists of which plants are found where in town. And so the next year, in my role as resource manager for the Friends of Princeton Open Space, I led many walks in various preserves to inventory the plant life. With help from a Princeton University summer intern, Sarah Chambliss, we compiled 22 plant inventories. 

I added many photos, and a section on invasive species, including mention of the emerald ash borer. Though the ash borer had yet to reach NJ in 2010, it has by now already killed most ash trees in our area, just 13 years later. 

To document some environmental history, I'll mention the following. The PEC, chaired by Wendy Kaczerski at the time, paid for the 2010 ERI using borough and township funds and a matching grant from The Association of NJ Environmental Commissions (ANJEC). The study was carried out by the Delaware Valley Regional Planning Commission (DVRPC), with input from the PEC and borough/township staff. 

Chris Linn of the DVRPC did most of the work to compile and write up the ERI. That document has served the town since it was published in January, 2010. Some of the acknowledgements are below. Looking at the names now--among them Rosemary Blair, Grace Sinden, Casey Lambert, Vicki Bergman, Greg O'Neil, Charles Rojer, Wanda Gunning, Gail Ullman, Ted Thomas--brings back good memories and is a reminder of how deep are the roots of environmental advocacy in Princeton.