In the 1960s, entomologists began to suspect that a decline in some insect species might indicate a trend. At the time there were no longterm studies to establish if that was true.
Researchers began collecting samples of multiple insect species and logging each year’s totals. By the1980s the trend was taking an ominous shape. Bug numbers were declining, dramatically.
Insects have a crucial role in Earth’s biosphere. Their total mass exceeds that of all vertebrates combined or about 70 times that of humans. They play a key role consuming and being consumed in the food chain. They pollinate flowering plants. They aerate the soil. Birds, bats, and many animals depend on them for food. They are even a nutrient-rich food source for humans in many parts of the world. There are over 300 species of plants that feed on insects.
Some of the earliest animal life on land were insects, paving the way for other terrestrial fauna. Their role is vital to our own food chain.
Recent insect population studies around the world have more clearly defined the trend, suspected over half a century ago. Declining insect populations have placed the world on a path to “ecological Armageddon,” according to several studies.
Since 1989, researchers from Raboud University in the Netherlands documented insect population decreases in nature reserves across Germany. Nature reserves were chosen because humans would have the least direct influence on insect numbers. They found that there was a decline of 75 percents over the 27-year study. During the summer months, the decline averaged around 82 percent.
What would happen in regions where human influence was greater? Research in this area has begun to gain importance and urgency.
Species-specific studies show similar losses. For example, agricultural production is threatened by a loss of pollinator species. Orchardists have suffered losses in production because pollinating insect species have declined. In Europe and the U.S., a 30 to 40 percent reduction in wild and managed bee populations has been documented. This is called colony collapse disorder. A decline in some species of butterflies is beginning to show up in peer-reviewed journals and the media. Many protected species show similar rates of decline.
A 2014 study published in Science documented a steep drop globally in insect and invertebrate populations. Rudolfo Dirzo, an ecologist at Stanford University, says, “Although invertebrates are the least well-evaluated faunal group within the International Union of Conservation of Nature (IUCN) database, the available information suggests a dire situation in many parts of the world.”
A significant drop in insect populations would have far-reaching consequences for humans and thousands of other species. A 2010 study by Canadian biologists suggests that insect feeding birds in North America have suffered more pronounced declines in recent years than seed-eating species.
The populations of birds and insects are closely linked to human health. Mosquitos are not the only insects that carry diseases. Being able to control disease-transmitting insects depends upon healthy populations of birds and bats. The result is that a decrease in overall insect populations also results in a decline in insect predators (birds, bats, amphibians, and predator insects). This, in turn, removes much of the control of vector insects like Anopheles mosquitoes (vector for malaria). Other diseases carried by mosquitos include encephalitis, West Nile virus, dengue, yellow fever, filariasis, tularemia, dirofilariasis and Zika.
An alliance of 22 publicly funded environmental research institutions has compiled a list of ecosystem services provided by insects. The group concludes, “over three-quarters of wild flowering plant species in temperate regions need pollination by animals like insects to develop their fruits and seeds fully.”
Not only birds and bats control disease-vector insects. Germany’s Federal Agency for Nature Conservation has identified long-legged flies, dance flies, dagger flies, and balloon flies as important predators for pest insect species. Spiders are not insects but they too play a role in controlling pest insects.
It is becoming abundantly clear that as the human population grows, so does the need for more food production, pest and vector control. Chemical pesticides are a solution with widespread collateral damage to ecosystems. Indiscriminate use of wide spectrum pesticides kills both pest and beneficial species.
A long list of factors that contribute to insect loss was compiled by the Berlin Natural History Museum. For example, the widespread overuse of nitrogen fertilizer may help one plant species to thrive, but prove toxic to other plant species and beneficial insects.
Ecologists who look at this problem identify many factors at work. A few of these factors identified in the literature deal with climate change, habitat destruction, deforestation, fragmentation, urbanization, agricultural conversion and chemical pollution.
This new evidence points to the importance of increased research in the field and the opportunity for “citizen science” projects where lay people with an interest in the outdoors can be trained to collect important data.
Long-term global data comparisons are scarce and in many places non-existent.
The decline in overall insect populations is just one more of many threats coming to a head in the first half of the 21st century. This and half a dozen others are each capable of compromising our own global civilization. Failure to respond to these challenges appropriately could result in our own “colony collapse.”
W. Douglas Smith is an environmental scientist, environmental diplomat, explorer, educator and a retired Senior Compliance Investigator for the U.S. Environmental Protection Agency, where he worked for 36 years.