The intersection of habitat loss and climate change

The insect world is undergoing dramatic changes and that has big ramifications for all of us

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few years ago, it electrified the world when someone somewhere, declared an “insect apocalypse,” the ignominious end of all those tiny creatures on whom we daily depend, of whom we take virtually no notice, and who all by themselves make up the vast majority of the animal kingdom.

It’s a joke among entomologists that, within a margin of error, all animals are insects. When you examine the hopeless complexity of global biodiversity, us mammals are a rounding error when compared to the beasts beneath our boots. There are more species of beetle than species in any other category, and at any given time, there are an estimated 10 quintillion insects on planet Earth, putting our global population of 7.8 billion into comical context.

The idea that these multitudes of pollinators, recyclers, and soil engineers (“the movers and shakers of the biosphere” in the words of population ecologist Soren Bondrup-Nielsen) were in the grips of universal collapse, captured public imagination in ways previously impossible for this class of animal. Suddenly, the masses of creepy crawlies we’ve reviled for generations became the subject of intense consideration and sympathy, an important and overdue shift in public perspective, though perhaps thanks to misleading language.

“Like many entomologists,” says David McCorquodale of Cape Breton University, “I see the claims of an insect apocalypse as absurd.”

In 2017 when a group of researchers published a paper in the journal Plos One that concluded that, between 1989 and 2016, the biomass of flying insects in German protected areas dropped 76%. Then in October 2018, another paper came from the Proceedings of the National Academy of Sciences, demonstrating an even more staggering 98% decline in the biomass of ground insects in Puerto Rico’s El Yunque National Forest reserve since the mid-1970s.

These are sobering results and deserve serious consideration but whenever you hear claims of an insect apocalypse people will cite these two papers, the same two data points serving time and again as journalistic mic-drops. And that’s what bothers David McCorquodale.

He says we cannot use isolated and extreme insect declines in some regions as evidence of global collapse. It would be like tracking the declines of Woodland caribou in Atlantic Canada, Grizzly bears in Yellowstone National Park and Northern White rhinos in Kenya, then using these results to declare a “mammalian apocalypse,” when in fact many mammals are doing just fine. You simply cannot lump the largest, most widespread and most diverse family of animals on the planet under a single sweeping phrase like “insect apocalypse.”

Biology professor Jeremy Kerr of Ottawa University studies biodiversity loss, concluding that insects are not enduring a unique collapse when compared to the rest of wildlife. They’re just another player in the same mass extinction impacting the rest of the biosphere, with winners and losers depending on the needs of each individual species. Some insects appear resilient to the changes we’ve wrought on this planet. Many aren’t.

“If we say there are places where biodiversity has declined very dramatically [like Germany], there are also lots of other places where it has not,” says Kerr, referencing the north Boreal forest, just below the Arctic Circle. “If we look at the overall picture—not extrapolating from Puerto Rico to planet Earth—do we have evidence of serious [insect] declines? The answer is yes. Do we have evidence of declines that resemble what Puerto Rico seems to have experienced in this one high altitude forest reserve? The answer is clearly no.”

Canadian insects aren’t collapsing in harmony. Instead, like birds, mammals, fish, amphibians and reptiles, insects persist but are taking losses.

When broaching the decline of Canadian insects, I always think back to my 2018 interview with retired coleopterist and lepidopterist (beetles and butterflies respectively) Reggie Webster, who has more than doubled the known number of beetles in New Brunswick over the last 15 years, taking the province’s tally from 1,200 species to over 3,000 using just his free time and home laboratory.

“I’m quite sure a number of these will be new to science,” he says. Your average Canadian might assume the discovery of a new species is a big deal, but not so with insects. There are still some wide gaps, even in well known taxa like bees, several dozen new species of whom have been discovered in Canada since 2014.

“In Canada and North America generally, we are perhaps second only to Europe in terms of the amount of information we have on insects and how they’re doing,” explains pollination ecologist Nigel Raine of Guelph University. “Yet I’d still say that even in North America we have very patchy information and we’re still learning a huge amount about the insects around us and how they’re changing in response to all these different stress factors.”

Raine goes on to explain that simply discovering an insect and describing it in the literature, as Webster has done for his own amusement almost two decades now, still doesn’t tell us much about the ecology of the insect in question. What’s worse, there are precious few people like Webster who can help confirm the identity of these insects when they’re found elsewhere. The encyclopedia of insect life is colossal and no one on Earth has memorized more than a few chapters.

This is part of the reason predictions about the near future of insects are so impractical. There are so many species we have yet to identify, especially outside Europe and North America, and even those we’ve graced with a name are relative unknowns.

Two meta-analyses, published in the journals Biological Conservation and Science respectively, attempt to tackle this point. The first, published in April of 2019, concludes that 40% of the world’s insects could go extinct in the next few decades (on par with the expected losses of other groups of animal, specifically amphibians), whereas the second (much larger) analysis from April 2020, estimates a drop in insect abundance globally of 25% since 1990, again, not dissimilar to other groups of animal. The limitations of the data, as outlined above, have been acknowledged in both cases.

So, for an informative and useful glimpse into the health and trends of Canadian insects, we must consult the bugs we know best, and be careful about the conclusions we draw.

Jeremy Kerr of Ottawa University, who says earlier there are winners and losers in every corner of the biosphere these days, also says the insect declines we have observed in Canada tend to occur at the intersection of habitat loss and climate change.

Karner blue. Photo: Wikimedia Commons

The Karner blue is a butterfly once commonplace in Canada, enjoying a specialized relationship with the Wild lupine (Lupinus perennis), which is not the insanely prolific plant found in most gardens.

The Wild lupine is a more humble and fragile flower, so when we cleared its meadows for farmland, particularly in southern Ontario, it only grew in a few ditches and protected areas by the 1990s, dramatically shrinking the range of the dependent Karner blue. The butterfly itself disappeared from Canada entirely in 1991, when unseasonably hot weather its few remaining reserves of Wild lupine, drying up all available nectar. The butterfly persists, barely, in isolated pockets in the United States, but has never returned to Canada. And that’s the intersection of habitat loss and climate change.

Another example is the Monarch butterfly, once a sublime sign of spring and now a seasonal bad news story. Its staple food, milkweed, has been the target of agricultural repulsion for decades, becoming scarce and frustrating the survival of Monarchs throughout the continent. The fewer milkweeds prevail, the fewer Monarchs there are to weather the uncertainties of climatic change. Their population has plummeted over 90% in a couple decades and hasn’t yet shown signs of sustained improvement. Here again, habitat loss meets climate change.

When it comes to bumblebees, we all have the vague notion that pesticides are driving their disappearance, but the truth is considerably more complicated. While pesticides are a factor, conservation scientist Sheila Colla of York University puts the blame elsewhere.

There are just shy of 900 bee species native to Canada, of whom the most popular, and thus the easiest to study, are the bumblebees, numbering 42 species north of the border, about a quarter of whom are considered at risk.

“They’re kind of like the panda bears of the insect world,” says Colla, who assembled the first quantitative evidence of wild bumblebee declines in North America for her PhD, is the North American coordinator of the IUCN Red List of Threatened Species for continental bumblebees, and was the last person to see a Rusty-patched bumblebee in Canada.

This species went from being one of the most common species of bumblebee in Southern Ontario to the absolute rarest in 40 years. Colla found the last one in 2009 in Pinery Provincial Park. Incredibly, she spotted it through the window of a moving car. “At that point I’d been looking for it every summer since 2005,” she recalls.

The primary factors causing bumblebee decline in Canada, she says, are climate change, which destroys spring and fall food flowers with extreme cold and heat, and pathogen spillover from managed bees, chiefly honeybees.

Pesticides kill bees, she explains, but it’s important to note that a modern corn field or potato field or canola field, whether it’s been sprayed or not, is still terrible bee habitat. The lack of diversity among its flowering plants means that pollen is super available for very short periods of time and absent the remainder of the year, and, lacking any nesting habitat in the vicinity, like hedgerows, bumblebees are disincentivized to establish themselves on or near modern farms anyway.

To fill this pollination gap, managed hives of introduced European honeybees have become common, trucked into these fields and set to work distributing pollen in place of the evicted wild pollinators. Pesticides killing these introduced honeybees, says Colla, has resulted in the widespread narrative of pesticides and bee collapse.

Rusty-patched bee. Photo: USFWS

Managed honeybees carry several introduced pathogens which they spread among native bees. The Rusty-patched bumblebee, which Colla studied in the final days of its decline, disappeared so rapidly, even from habitats as remote as the Great Smoky Mountains, that she suspects they fell victim to just such a pathogen introduced by European honeybees. The only Rusty Patched bumblebees that survive today are in Minnesota, Wisconsin, and Iowa: farm country where pesticides reign supreme.

Once again, pesticides kill insects and neonicotinoid pesticides have proven especially harmful to bees with even mild exposures but these sprayed habitats were already forbidding to bees. Those species most vulnerable to climate related shifts in seasonal temperature, and to the pathogens of introduced honeybees, are the ones in serious decline, such as the Rusty-patched, Yellow-banded and American bumblebees, while others have proven remarkably resilient. The Common Eastern bumblebee has gone so far as to expand its range in recent years, questing into the Maritime provinces, perhaps filling a void.

Jeremy Kerr makes the point that the number of individual bumblebees in Canada, certainly in his backyard, hasn’t dropped that dramatically, at least not that we’ve quantified. What has dropped is the number of species, his backyard flowers now pollinated by one or two bumblebee species where once there might have been five or six. Mass extinction, which is a slow and evil process, weeds out diversity first. Winners and losers.

A final, informative decline among our native insects concerns the lady beetles, known commonly as ladybugs. In the Maritimes alone there are 51 recognized species, some of whom you wouldn’t give a second glance, others exuding strangeness and beauty not easily overlooked.

Denis Doucet has been many things over the years—zoologist, biologist, entomologist, and interpreter for research and conservation organizations—so it’s perhaps best to call him a naturalist and leave it at that.

While attending the entomology program of Université de Moncton, he look part in beetle collections around campus. In and around 1983, he says, the most common lady beetles identified by these catalogues were the Transverse lady beetle and the Two-spotted lady beetle (this one overwintering in people’s homes). In 1984, he started to see introduced species entering the catalogue, such as the Seven-Spotted lady beetle and Asian lady beetle. By 1987, the native Transverse lady beetle was gone.

Nowadays the lady beetles in your home, crawling on windows during sunny days, are more often than not exotic Asian Lady Beetles. Consult the Lady Beetles of Atlantic Canada project page on iNaturalist (an online citizen science website and smartphone app) and you’ll see that (as of the time of writing) there’s not a single entry of the Transverse lady beetle.

Transverse lady beetle. Photo: Wikimedia Commons

Of the top six species most often identified by this project, only two are native. In order of occurrence are the Asian lady beetle (exotic), Seven-spotted lady Beetle (exotic), Fourteen-spotted Lady beetle (exotic), Three-Banded Lady Beetle (native), Variegated lady beetle (exotic) and Eye-spotted lady beetle (native). The Two-spotted lady beetle, once a fixture of our lives, has been relegated to eighth place. Exotics have conquered the market.

While invasive insects have had spectacular consequences for Canadian forests, like the Emerald ash borer and Hemlock Woolly Adelgid, their impacts on other, native insects are poorly understood, and draw a great deal of Doucet’s concern.

If you’ve been concerned about the insect apocalypse, you don’t have my permission to calm down. We’re redefining a crisis, not debunking one. As with the remainder of the animal kingdom, our impositions on this planet (climate change, habitat destruction, invasive species, and the rest) are applying more pressure on some species than they can endure. The spike in public concern for insects is heartening and deserved, but widespread ignorance of insects caused us to misinterpret the evidence, and leap to off-base conclusions.

There are species of insect that aren’t in peril and there are others that will disappear without fast action. We cannot afford to misinterpret this issue, overvaluing or undervaluing a class of animal that requires the full force of academia to understand and of conservation to preserve intact. Step one is to recognize them instead as members of a broader community of life, with strengths and weaknesses, and a common struggle against the indiscretions of humanity.

This article was originally published in The National Observer.

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