Drink Tequila if You Want, but Then Go Plant for the Bugs
As insect numbers plummet worldwide, inaction isn't an option
From time to time, insects make the news. For example, the bark beetle has snagged headlines as its range has increased due to warming temperatures, leading to the decimation of large tracks of North American forests. Other wild invertebrates, like the western bumblebee, have attracted attention due to a pronounced decline in numbers. However, what has now come to light is that insects as a whole biological class — and including the most commonplace species — have been disappearing. Buzzing bugs likes flies, wasps, moths, and butterflies, once taken for granted in their ubiquitousness, are vanishing.
Photo by Dan (catching up), Flickr
In October, the journal PLOS published a study finding a 76 percent decline in flying insect biomass in Germany’s natural areas over a 27-year period, from 1989 to 2016. Researchers from Radboud University, University of Sussex, and Entomological Society Krefeld measured the changes in total biomass by setting Malaise traps — tent-like structures used to trap insects — in 63 nature protection areas. Researchers found the pattern of decline to be similar across the different locations. The changes in biomass varied between the seasons, with an 82 percent decline in mid-summer, when insects numbers are usually at their highest.
Prior to conducting the study, the research team was aware of documented declines in abundance of single insect species, but posited total insect biomass as an indicator of overall ecological health. Ultimately, the results of their study far exceed the average estimated decline of vertebrate species globally — a 58 percent decline — reported by the World Wildlife Fund’s 2016 Living Planet Report, which tracked the change in abundance of many living organisms between 1970 and 2012. This report and others that make reference to the sixth mass extinction currently underway, in which the planet is losing species at an unusually high rate, often focus on the loss of vertebrate species. The PLOS study indicates that invertebrates could be facing even steeper losses.
“Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and jeopardize ecosystem services,” wrote the study’s authors. “The widespread insect biomass decline is alarming, ever more so as all traps were placed in protected areas that are meant to preserve ecosystem functions and biodiversity.”
As insects are a crucial link in the food chain, the impacts will be devastating if rates of species decline continue unabated. It’s estimated that 80 percent of wild plants depend on insects for pollination and 60 percent of birds rely on insects as a food source. In the US alone, wild insects provide about $57 billion every year in “ecosystem services” including pollination of crops.
For Scott Black, executive director of Xerces Society for Invertebrate Conservation in Portland, Oregon, the PLOS findings confirmed observations that he and others who’ve dedicated their careers to insects have made for many years. Known as the “windshield phenomenon,” anecdotal reports of insects disappearing from view have been mounting. Two decades ago, as a youth living in Nebraska, Black would frequently take his Ford Mustang joyriding. This pastime was inevitably followed by car washing to remove the bug carcasses spattered on the windshield. A few years ago, Black drove the same vehicle during a visit to his home state and found no bug splatter — a trend noted by others from North America to Europe. Although skeptical of his own observations without supporting data, Black views the PLOS study — and many others showing steep declines in species of butterflies and wild bees — to be evidence of a dire problem.
“Historically we had been focusing on the decline of rare insect species and that may have been a mistake because we overlooked what was happening with more common species,” said Black. “We’re losing up to 85 to 95 percent of some common species. We’re generally seeing loss of flying insects. It’s difficult to nail down one cause because it’s really death by a thousand cuts.”
Climate change has generally been cited as a factor affecting insect populations and habitat, but the PLOS study found climate change alone to provide an unsatisfactory explanation of the major biomass decline. (Climate-related factors such as prolonged drought were not thoroughly analyzed.) The authors did conclude that the driving force behind the disappearance of so many insects from natural areas must be macro in scale. They also suspect that agricultural practices — particularly those utilizing insecticides — are a likely culprit. Caspar Hallman, the study’s lead author, stressed that further study is required to fully understand the phenomenon, but pointed out that the 63 study sites are representative of nature reserves interlocked within a modern agricultural landscape. Other factors could include anything from the expansion of suburban development and resulting habitat loss to the spread of disease.
As far as climate change goes, Black notes that warming temperatures will not impact all species the same way. It may give some insects a boost by allowing them to expand their range, while other impacts like droughts, wildfires, increased hurricane activity, and record-setting levels of precipitation could wipe out populations.
“There are going to be the haves and the have-nots,” Black expressed. “Some species are going to do well. Some butterflies are expanding their range but many more are losing both population and range. There’s been a great loss in both biodiversity and total biomass. Plants and insects are the fabric of the ecosystem, and without this fabric, most things don’t get to eat. This is really problematic.”
According to Wolfgang Wägele, director of the Leibniz Institute for Animal Biodiversity in Bonn, Germany, impacts from the loss of insects are already being experienced in parts of Europe where there’s been a pronounced decline in insect-feeding bird species and a drop in wild berry production in German forests. A rise in the number of orchids that fail to produce seeds has also been observed. Some orchid species like the bee orchid and the fly orchid rely on relationships with specific insects for pollination. In the absence of those insects, the orchids fail to produce seeds. Since a broad spectrum of insects are affected, he expects to see an overall decline in flowering plants, slower decomposition of leaf litter, fewer bats and other small mammals that feed on bugs, and less natural control of pest insects. And these impacts extend beyond Europe — similar trends have been observed from the United States to the Middle East.
“Our hypothesis is that the phenomenon is a global one and that insects die in all regions where modern, very efficient pesticides are being used in agriculture,” he said. “Dramatic losses occur in tropical areas, where rainforests are being destroyed rapidly, and then pesticides are used to combat insects in the new arable fields.”
“We need new laws that allow [us] to control the effects pesticides have at the landscape level,” Wägele added. “Every citizen who possesses a piece of land can help: Do not use pesticides, don’t cover front gardens with nice pebbles or synthetic turf. Let the native plants grow in some corners of your garden and don’t plant only ornamental plants that are worthless from an ecological point of view.”
Though Black says additional research on insect decline outside of the temperate regions would be useful, he notes that we have plenty of information to take informed action.
“These results make you want to drink tequila until you drop but we can still work to restore and manage habitat as best we can to protect biodiversity and biomass,” he said. “We can change how we eat, change the urban landscape and adopt more sustainable ways of growing food. It makes me want to step up because it’s not productive to do nothing. Conservation has been my entire life and I’m going to do all that I can. We shouldn’t just let these studies pass by without taking action.”