Thursday, September 30, 2021

Where Have All the Pollinators Gone? -- Summer, 2021

Wherein is discussed the season's paucity of pollinators, the curiously prolific presence of hornets, and possible causes thereof. 

With the coming and the going of this year's autumnal equinox, it's time to look back on a long summer and ask, "What happened?" Or, more precisely, "What happened to the happening that didn't happen?" 

There's lots of talk about how insects are in decline and that we need to plant more wildflowers to support them. A local ecologist and avid birder, David Wilcove, co-wrote an oped in the Washington Post about the danger posed by insect decline, and the need to better monitor populations, as is done with birds.

In past years, a summer's climactic buzzfest on the boneset

This year, there was a steep decline in pollinator numbers in Princeton. Each year I grow a banquet of wildflowers in my backyard for all manner of insects to feast upon. In past years, they'd come from near and far, their numbers building through summer, climaxing in late August in a buzzfest on the boneset. Though mountain mint is another great draw for insects, in my yard it was boneset in particular, clustered here and there in the garden, that in past years drew the multitudinous shapes and sizes of the insect world. Its broad disks of tiny white flowers seemed like a Serengeti in miniature, an open plain perched conveniently four feet above the ground, teaming with life. It was a chance to see the insects close up, they being so focused on the nectar or each other that they took little notice of me.

Then, two years ago, and again last year, the numbers of insects were down--still numerous but not enough to stir that late-summer's jazzy feeling of frenzied activity. 

2021: An astonishing diminishment

And this year? This year, boosted by the rains, the wildflowers grew to fabulous size. Broad arrays of blooms mounted on multiple stems stood at the ready. In early summer, while periodical cicadas held center stage, the numbers and variety of pollinators were building nicely. 



But then, as the wildflower meadow's heavy hitters--the cutleaf coneflowers, Joe-Pye-Weeds, bonesets and wild sennas--unveiled their fabulous blooms for the mid-summer festival of nectar, the insects were no-shows. Abundant flowers had few pollinators, and sometimes none at all. Diversity dwindled to some tiny somethings, a few bumblebees and even fewer honey bees. 

Sifting through possible causes for the decline

Possible causes for the dramatic decline have been offered: extreme heat, more homeowners fogging their yards for mosquitoes, expanding monocultures of lawn and invasive species. Or perhaps the climate-changed winters have messed with insect dormancy.

The rains of July, the rains of August

What I have particularly noticed over the past three years, however, is the increase in rain during the summer. Rutgers precipitation data for NJ show increased precipitation particularly over the past two years in July and August. Not only has there been more rain, but the intensity of the rain has increased. The sound on the roof is different--one can hear and even feel the extraordinary density and weight of the rain. The deep trauma of Hurricane Ida was the climax among multiple intense storms before and after. The ground and foliage are literally getting beaten up by these deluges. Insects try to hide during storms. Some live in the ground. The harder the rain, the fewer places to hide, and the more likelihood that a ground nest will be flooded out. All that sustained moisture could increase the risk of disease, which an entomologist friend says can play a big role in bee numbers. 

Some of us noticed other changes as well. Gladly, the numbers of odorous house ants invading our kitchen were down from previous years. Mosquitoes in our area seemed relatively rare in early summer, though numbers surged later in the season--tiny ones, probably asian tiger mosquitoes. 

A proliferation of hornets

What was most striking and very strange was a proliferation of hornets. Last year, I seldom saw them, but oftentimes this summer, approaching a patch of flowers, the first thing that would catch my eye was not pollinators but the hornets that can prey upon them. 

We have two kinds of insects called hornets. One is the European hornet, which looks to me like a stocky bee--black markings with a particularly thick yellow abdomen.

The other is the bald-faced hornet, a native insect with black markings and a whitish face. 

Both are hard to photograph because they don't land, but instead keep cruising around the flowers. Periodically they may bump into a bee that was minding its own business on a flower. The contact lasts a split second, then the hornet flies on. The purpose of this brief harassment is not clear. 

Here's a bald-faced hornet in adult and larval form, found on a fragrant of nest someone left at the curb. Both kinds of hornets live in nests that are in or hang from trees. The paper they make, by the way, is beautiful when looked at close up.

Why the proliferation of hornets, cruising relentlessly among the flowers with a sense of urgency but no clear goal? Maybe they just seemed more numerous due to the lack of other insects to catch one's attention. Or maybe the fact that they live in elevated, waterproof nests allowed them to better survive the intense storms. 

The seeds of change planted over centuries

In any case, this summer was not the lively pollinator party I was used to playing host to, both in my backyard and at our Botanical Art Garden (the "Barden") in Herrontown Woods. One interpretation is that the carbon dioxide we've been scattering to the winds is now coming home to roost, in the form of weird winters and intensified storms. In Princeton, basements flooded that had never flooded before. It's not a stretch to hypothesize that many bees also find themselves newly vulnerable to the merciless power of the rain. And then, on the sunny days when pollinators can make it to the flowers, there's the haunting background of patrolling hornets.

In a docile wasp, some small comfort

As students returned to the university, I remembered helping my daughter move in to Whitman College two years ago. In the courtyard, I had noticed thousands of wasps cruising just above the grass. It was a mating dance, of no danger to the parents and students passing by, of blue-winged wasps. I had recognized their distinctive orange abdomen from those that would frequent the flowers in my backyard, a mile away from campus. 

This year, I had seen only one in my yard, and wondered whether their improbable annual ritual was still playing out at Whitman College. 

What I found on Sept 2nd were perhaps a hundred wasps flying in their usual criss-cross manner a foot above the lawn. Some seemed fatigued by it all, and would abandon their flight to sit among the grass blades for awhile. Though their numbers were down from the thousands I'd seen two years prior, I was glad to see any at all. And a student sitting in a lawn chair, scrutinizing his computer, told me there had been many more ten days prior when students first began moving in. 

It would be nice to think that the paucity of pollinators I observed this summer was an isolated affair. But others around New Jersey have made similar reports. An entomologist friend who lives in Oregon told me that he's seen "a very significant decline in pollinators" this year, probably due to drought, though he also said that each species can vary in numbers year to year. 

An ark is built of something more than flowers

We take so much for granted in our lives. When something breaks, that's when one has to study up and figure out how it works, what went wrong, and how possibly to fix it. The insect world has been taken for granted since forever. Annual bird surveys benefit from a community of avid birders, but citizen scientists who are up to speed on the mind-boggling diversity of insects are fewer to come by. We thought we could just plant some flowers and the insects would come, but the needs appear to be far deeper than that. 

Sunday, September 19, 2021

Mile-a-Minute Spreading into Princeton

 One of the more noxious invasive plants that has been spreading across NJ is Mile-a-Minute. It's a prickly vine that, though an annual that must grow back from seed each spring, grows so fast that it can cover large areas of roadsides and field edges. Over the past several years, I've been knocking out small infestations at the Princeton Battlefield and near Rogers Refuge, but this year I'm finding new patches springing up around town.

Then, driving my daughter to MarketFair along Canal Pointe Blvd a week ago, I saw a massive infestation that surely is a major source of the seeds that birds are then spreading across Princeton. 

The vine has a distinctive triangular leaf. Berries are just beginning to ripen. If you encounter it, put some gloves on, pull it out and put it in the trash. Putting it in the compost would allow the seeds to spread. 




The infestation along Canal Pointe Blvd is behind 701 Carnegie Center Drive. In the aerial, you can see rows of solar panels over the parking lot. To the left of the solar panels is a big mowed lawn, and to the left of the lawn in the photo is the unmowed land upon which the Mile a Minute is growing. My friend Peter researched the owner, which on the deed appears to be "BXP Carnegie Owner, LLC%G". The land has a farm easement, so is only valued at $39,000, which means the owner is paying next to no taxes to hold very valuable property, meanwhile expediting the spread of Mile a Minute and the associated nuisance it will cause. 

It's hard to photograph the cocktail of invasive species at the site. The white flowers are of white snakeroot, a native wildflower, which is besieged by a layer cake of stiltgrass, porcelainberry, and Mile a Minute climbing on top of it all. 

Further down the road is a series of trees damaged, perhaps by a small tornado or similar localized intense winds as the remains of Hurricane Ida came through on Sept. 1. Similar damage to trees was seen in Princeton Battlefield, where a row of mature white pines along the edge of the field was decapitated.

What we're seeing is the increasing impact of plants out of place (species that turn invasive after being introduced from other continents) and carbon out of place (carbon fuels extracted from underground that we burn, thereby releasing additional carbon dioxide into the atmosphere). Our machines have increased global warming CO2 by a whopping 50% over pre-industrial levels thus far. This year has felt like a radicalization of both invasive species and climate change. 

Treepedia Author to Speak at Veblen House--Sept. 24

Come this Friday, Sept. 24 at 6pm, for a free event next to Veblen House in Princeton. Author Joan Maloof is coming to Herrontown Woods to discuss her new book, Treepedia: A Brief Compendium of Arboreal Lore. The book has 100 short but stimulating profiles of extraordinary trees, forests, and the people working to protect them. 

The event will take place on the wooded grounds of Veblen House. The Friends of Herrontown Woods is hosting the event, which is sponsored by the Princeton Environmental Film Festival.

We're looking forward to meeting Joan and hearing about her book!




Labyrinth Books will be on hand at the event with copies of the book as well.



Saturday, September 18, 2021

Butler Tract Meadows Restoration?

This is the story of what can go wrong if you plant a native meadow and then don't take care of it. Princeton University has been installing some native meadows, and some have done a lot better than others.

Just off of South Harrison Street, framed by Sycamore Rd and Hartley Ave, are some meadows that were planted in 2016 following the university's demolition of the Butler apartments. It was a well intended succession from graduate housing to native meadow, and when I took a look in 2019, the meadows were still hosting diverse native wildflowers. 

Two years later, these signs appeared: 
"Butler Tract Meadows is under an invasive management program for this year."

For most of the summer, it wasn't clear what that meant. The signs appeared early in the growing season, but I could find no sign of any action. 

 

This photo tells the story of what happened to the native meadow over the course of five years. The usual nonnative invasive species moved in and began to dominate, with mugwort foremost among them. The white flowering plant on the left is Japanese knotweed, which can form large monocultures as well. Bamboo is getting a foothold in the lower lefthand corner of the photo, and in the distance can be seen the sproutings of black locust, a native tree that nonetheless can move aggressively into native grasslands. 

Sericea lespedeza (L. cuneata) is another super-aggressive nonnative. Newer on the Princeton scene, it can rival mugwort in its capacity to displace diverse native plants, for instance along the gasline right of way that crosses the Princeton Ridge. 
And here's crown vetch, which climbs over everything around it. Both crown vetch and Sericea lespedeza were planted extensively along freeways to control soil erosion, reducing one environmental harm while creating another. 

I did notice a few native species still present, including this wild senna. The only practical means of shifting the balance back to the native species on this scale is through use of herbicides. Some people lump all herbicides together and pronounce them evil poisons--an indiscriminate rejection borne of their often indiscriminate use. But there are many kinds and many formulations, some far safer than others, and the aim as with medicines for people is to use as little as possible, in a targeted way. 

The way to reduce the use of herbicides is to be proactive and intervene early to kill the invasives when they are still few in number. That would have been something to do from the beginning, back when a more targeted, minimalist approach was possible. 



My friend Basha who lives across from the Butler Tract told me they had finally done some spraying. A week later, I took a look. Here you can see the black locust tree sprouts turning brown while many other invasive plants appear untouched.
This big patch of mugwort shows some sign of dieback, but pretty uneven results thus far.
I'm guessing that patch in the background of this photo was crown vetch. In the foreground is probably common cinquefoil (Potentilla simplex), which is native but a very rapid spreader.

It will be interesting to see how this goes. My experience is that institutions have always understood that lawns and landscaping take ongoing care, but they have yet to grasp that more naturalistic areas like meadows also need ongoing intervention. At the Butler Tract, they seem to be trying to figure out what that means.


Sunday, September 12, 2021

Nature's "Depressions" Bring Beauty and Resilience

Another in my writings about the ecological, logistical, and psychological aspects of tending to a detention basin at Smoyer Park that we converted into a native meadow. Most of the photos and writing are from mid-July, 2021.

There's a garden that many people pass by but few notice. I saw my second monarch butterfly of the season there in mid-July, attracted to the subtle flowering going on there. It's at the far end of the parking lot in Smoyer Park, out Snowden Lane. Drive or bike down to the lower end of the lot, and by heading downhill, you're essentially following the water, doing what rain does after it hits the ground. And there you will find what most people, if they have any name for it at all, will call a detention basin, so-called because it detains runoff, slowing it down, capturing it in a depression so that it can seep into the ground and feed the aquifer rather than feed a flood.

Bureaucracies require it, engineers designed it, but probably none of them were thinking about what a great place this wet, sunny spot would be to grow native plants. That came later, when another arm of the government, Partners for Fish and Wildlife, worked with me and the town to turn this previously mowed space into what could more aptly be called a wild garden, or a wetland garden, or a wet meadow. 

"Depression" is a word that in psychology may have a negative connotation, and extended depression is surely something one would want to cure. But if you're an artist of some sort, a depression may mean the mind is doing important work at a very deep level, putting things together in a new way that may lead to a burst of creativity, insight, or both. To experience highs, one must be able to experience lows. 

Nature, too, needs its lows, even though depressions in the ground, too, tend to get a bad rap. "Drain the swamp" is a politician's stirring call to clean up the mess inside the beltway, and lots of swamps were drained when they got in the way of expanding our towns, cities, and farms. But as with people, a depression is where nature does some of its deepest thinking and finest work, feeding the aquifer and laying the foundation for foodchains with a rich variety of native plants. Gardeners like to lift plants up in raised beds, but many native wildflowers prefer the opposite, somewhere low down. Those are the seedheads of big bluestem in the photo, a dominant prairie grass in tallgrass prairies of the midwest, historically munched on by bison. 

You can see a fence bordering one of the ballfields at Smoyer Park in the distance, and most of the surprisingly many detention basins scattered across the Princeton landscape, in developments or at parks, are managed like a ballfield, with grass mowed to the ground, though no one would think to play a game there. One thing I've managed to do in town is get some of these converted to wet meadows--first at Farmview Fields, then at Princeton High School, then at Greenway Meadows and Smoyer Park. 

I walked through the Smoyer Park wet meadow in mid-July, to see how it's doing and to do some weeding of this half-acre wild garden. As any gardener knows, there's a lot that can go wrong, even in a meadow that's supposed to grow naturally. Many of these raingarden-like plantings, if untended, fill with a host of aggressive weeds, like mugwort, Canada thistle, and Chinese bushclover (also called Sericea lespedeza). Even natives like blackberry and some kinds of goldenrods can tend to take over.

Nature is complex, which can be daunting and even off-putting, or exciting for those who take an interest and build familiarity one plant at a time. That's where love comes in, because when you love something, you want to know everything about it. Botanists talk about plants like a baseball fan might take pleasure in quoting obscure statistics or reminiscing about certain players. Love turns complexity into joy. Love is also what gets one out there to check up on a wild garden, to make sure it's doing okay.

Knowing how much can go wrong can increase the pleasure at seeing so much going right. Now, this photo shows little in the way of blooms, but a gardener conversant with the species of a wild meadow can experience joy even before plants flower, is moved as much by what will be as what already is. Each stem of a favorite wildflower implies a bud, each bud a flower, and each flower a host of insects that in turn support a foodchain of wild life. 

A botanist gardener can see in this photo the spray of monkeyflowers in the lower left, the burst of rose mallow hibiscus in the center right, and behind them a favorite sedge called woolgrass rising towards maturity. Other species, too, are gaining in number and moving towards bloom--ironweed, partridge pea, blue vervain. From evidence of browsed stems, even the deer's appetites seem in balance, leaving many plants to grow unhindered. The diverse mix of sizes and textures triggers memories of other rich meadows seen--prairies in Ann Arbor, MI, Durham, NC, Chicago. How many people get to travel back in time and across half a continent, just by weeding a detention basin in a park in Princeton? 

Occasionally, a less sanguine thought can intrude. What difference does it make that a half acre meadow is prospering, when a whole planet is so quickly being overheated? Delight in mid-July could not completely eclipse news heard earlier that day, of environmental and cultural devastation in Europe, as an overheated atmosphere unleashed a flood that shattered all records. 

September 12, 2021

Since mid-July, Princeton had its own megaflood when Hurricane Ida swept through the night of Sept. 1. Basements flooded that had never flooded before. The DR Canal towpath was badly damaged, ten years after being similarly damaged by Hurricane Irene, and only two years after being fitted with a fresh cinder surface for walking, biking, and jogging. 

But one place I didn't worry about getting flooded was the detention basin at Smoyer Park. It's built for flooding, and fitted with native plants that have evolved to thrive on periodic floods. Though, being the caretaker, I will be worrying about whether I could be doing more to limit the spread of stiltgrass, carpgrass, canada thistle, blackberry, and various other overly aggressive species, to a passerby the meadow has a late-summer look of subtle earth tone radiance and balance. The white in the distance is late-flowering thoroughwort, mixing with the emerging yellows of goldenrod, a few lingering spikes of purple from the ironweed, and the bronze of tallgrass prairie species--big bluestem and Indian grass. 


Last year's post about Smoyer Park's basin: The Work Behind a Natural-Looking Meadow

Thursday, September 09, 2021

A Summer-Long Residency of Paper Wasps in My Window

Our house is solid, but for some reason there is one storm window that is slightly out of square--just enough that the storm window can't be fully closed. And through that small crack each spring come paper wasps, not to enter the house but to build a nest in the space between inner and outer windows. It starts with a queen--a kind of homesteader, or who in the business world might be called an entrepreneur. I haven't watched closely enough to see if she uses last year's honeycomb of cells or builds new, but at any rate she does the early work herself, as if starting a colony, or a small business, until she can raise young to do most of the work for the rest of the summer. Occasionally I'd take a look to see how they were doing.


The most common species of paper wasp, it turns out, is originally from Europe. A simple distinction between bees and wasps is that bees are vegetarians and wasps are carnivores. Bees raise their young on protein-rich plant pollen, while wasps feed their young other insects. 

My best guess as to what's going on in this picture is that the three wasps with their abdomens sticking out are feeding the young by delivering them food in their chambers. When ready, the larvae cap their chambers, pupate, and then eat their way out as fully formed adults. 

Some types of insects, like butterflies and cicadas, have to remain still after emerging, to let their wings slowly expand and dry. But these wasps emerge with their small, narrow wings ready to go. You can see one of the new wasps at the bottom of the photo, emerging like a chick from an egg. 

One day in July, I heard a scuffling sound at the window, looked up, 

and saw a bird balancing on top of the window. 
It was a red-bellied woodpecker--a bird named after a part of the body one almost never sees, rather than the red hood that is so distinctive.  From its precarious perch just above the crack in the window, it could use its keen eye, flexible neck, and lightning quick reflexes to snatch any wasps coming or going.
Sometimes it stuck its beak right in the crack, as if my house were a tree. 

Finally, the bird noticed me and flew off. Whether this was a singular visit or one of many, the wasp nest was considerably diminished and never regained its earlier hustle and bustle. By the end of August the nest stood empty, which meant I could now open the inside window again.

There are many questions to ask. Do the wasps feed their young regurgitated insect puree, or do they serve sliced and diced versions? Inquiring minds want to know. I spent some time trying to figure out which one was the queen. No wasp stood out as distinctly different from the next. Some of the wasps on the nest were vibrating their abdomens. Others were not. What does this mean? And what impact do the paper wasps have on my garden? Are they responsible for keeping my kale unexpectedly free of caterpillars, and if so, do they nicely limit their diet to garden pests, or are they also preying on the rarer sorts of butterflies and moths we wish there were more of? 

I found a few answers at this Galveston County master gardener site. Here are some excerpts:

Adult paper wasps are efficient predators, mostly of caterpillars. They carry them back to the nest and feed them to the developing larvae. They will collect large numbers of caterpillars from the area around the nest during the course of a season. Adult wasps typically prey on a wide variety of caterpillars including corn earworms, armyworms, loopers, and hornworms. Adult wasps also utilize beetle larvae and flies as food for their young..

Adult paper wasps primarily feed on nectar or other sugary solutions such as honeydew and the juices of ripe fruits. Adults also feed on bits of caterpillars or flies that are caught and partially chewed before presenting to their young.

and:

In early fall, the colony begins to produce males and special reproductive female wasps. These reproductive females, which constitute next year�s queens, mate with males and soon leave the nest in search of protected spots in which they spend the winter. The remaining worker wasps eventually die and the nest becomes vacant. Paper wasps will not reuse their nests the next year.

Even some websites that are trying to sell products or pest control services have useful info, such as this comparison of paper wasps and yellow jackets

I sometimes think of fixing the window, but I suspect that, come next spring, a lone queen of the paper wasp variety will come along and still find a suitable spot to take up residence. Maybe that's for the best.

Wednesday, September 08, 2021

Hurricane Damages DR Canal Towpath--Again

Driving into Princeton the morning after Hurricane Ida swept through, my first thought was to check Princeton High School. Had the school flooded yet again, ruining the performing arts stage for a third time? Fortunately not, judging from appearances as I peered in the windows. 

My next thought was the towpath along the DR Canal. Ten years ago, almost to the day, Hurricane Irene rendered the popular towpath almost unusable for walking, jogging, and biking, eroding it in places, coating its cinder surface with mud in others. Full repair, probably with FEMA money, was not completed until 2019--eight years later.

This is what I found after Hurricane Ida. A combination of fallen trees and thick mud have rendered sections of the towpath impassible, only two years after it was resurfaced.






Here's a closeup of the flood's deposits of silt that walkers and bikers encountered.
While some areas were covered in mud, others were scoured, stripped of the cinder surface that made for a comfortable walk.

At Rogers Refuge, the hidden floodplain preserve upstream of Carnegie Lake, a plaque marking the high water mark ten years ago was exceeded by an inch by Hurricane Ida. 

Elsewhere in Princeton, Mountain Lakes reportedly sustained damage to its bridges. In Herrontown Woods, the trails remained in good condition, but the power of the rain and runoff was evident in the widespread scouring of ground and the flattened vegetation. 

As our machines pour more CO2 into the air, the warmed atmosphere can hold more water, leading to rains that are extraordinary in their density and weight. The raising of CO2 levels by 50% represents a militarization of the atmosphere, where clouds can now carry tremendously heavy payloads of water. 

The need to build and maintain more and better waterbars to divert runoff from trails--a local form of "climate resilience"--is only adding to the workload faced by the largely volunteer organizations that care for Princeton's open space. More than a decade ago, working on habitat restoration at Mountain Lakes, I began thinking of climate change as a dark cloud on the horizon threatening to cast a shadow over our work in local preserves. The incredibly heavy rains are one example of how what once was foreboding has become a reality. 

Of course, one reason so little is being done about climate change is that the episodes of extreme weather quickly pass, segueing often into pleasant weather. Hurricane Ida seemed to sweep away the hot, humid summer, leaving in its wake refreshingly cool air. 

This hurricane's most lasting legacy may be a change in our relationship to water, perhaps the beginning of a retreat from the shorelines we so dearly love. The plight and uncertain future of the towpath--that wonderful waterfront trail--is only the most dramatic example of how a climate of our own collective making is beginning to threaten that which we hold dear.