Natural riparian and upland habitats support healthy species diversity and provide a wide range of services to local communities. The featured image shows one of the many streams that connect the lakes and rivers of the Boundary Waters in northeastern Minnesota (Photo: Kabetogama State Forest near Orr, MN. Credit: Michael Baumann).
Source Article: “Worldwide decline of the entomofauna: A review of its drivers” by Francisco Sánchez-Bayo and Kris Wyckhuys in Biological Conservation (2019) DOI: https://doi.org/10.1016/j.biocon.2019.01.020
A new review by Francisco Sánchez-Bayo (The University of Sydney) and Kris Wyckhuys (University of Queensland) has received attention from large media outlets including The Guardian, USA TODAY, CNN, BBC, and others. The researchers from Australia present a comprehensive review of historical reports documenting insect declines worldwide.
Their results reveal that current rates of decline put 40% of the world’s insect species on a path toward extinction and the timetable for the projections is what sounds such a deafening alarm – it’s several decades, not centuries or millennia.
In terrestrial ecosystems, Lepidoptera (moths and butterflies), Hymenoptera (bumble bees, honey bees, other wild bees, wasps, and ants), and dung beetles appear to be most affected. Together, these species represent an important fraction of all pollinators. This group of animals, which also includes birds, bats, and other small mammals, is responsible for one third of all food we eat. Pollinators sustain ecosystems and help plants and trees reproduce. In addition to aiding in the production of fruits, vegetables, nuts, oils, fibers, and raw materials, pollinators provide other valuable services such as preventing soil erosion, increasing carbon storage, and facilitating nutrient regeneration.
The majority of the studies identified in the report are from Europe and to a lesser extent North America. However, despite data gaps in large regions such as South America and Asia, modern insect extinction is outpacing vertebrate extinction by a large margin. Because the observed declines affect the majority of species in all taxa, we are amidst the greatest extinction since the late Permian (~250 million years ago) and late Cretaceous (65 million years ago – think dinosaurs) periods.
The declines in terrestrial and aquatic insects affect both specialist and generalist species. Specialist species thrive only within a narrow window of environmental variables such as a specific plant type or a limited geographic range while generalists make use of a variety of different resources and thrive in a wider range of environmental conditions. Certain more tolerant and, sometimes, non-native generalist species can fill the vacuum left by these declines. This form of species replacement can help ecosystems retain some level of function, though it’s not clear if they can sustain their provision of services. The expansion of more tolerant species is also not enough to offset losses.
Half of the studies analyzed in the review point to habitat change as the primary factor in insect declines, followed by pollution, biological factors, and climate change. Here, we’ll focus on the two largest factors as they are inherently linked.
Natural habitat has been decreasing over the past couple centuries and land continues to be transformed to make way for urban expansion, crop growth, and manufacturing of goods.
According to the United Nations, cropland covers about 12% of total land area on earth. The conversion of natural lands to farming directly impacts many species. Further, major declines occurred when low-input farming practices were upscaled and industrialized by the Green Revolution. With the intensification of farming practices came the use of genetically-uniform monocultures, the widespread application of synthetic fertilizers and pesticides, removal of buffering trees and hedgerows, and modification of surface waters to improve irrigation and drainage. Combined, all of these practices act to simplify terrestrial and aquatic species assemblages, particularly among specialist pollinators and beetles, and create a more homogenized and nutrient-depleted landscape.
Pollution in the form of fertilizers and pesticides used in agriculture, sewage and landfill contamination from urban areas, and industrial chemicals is the second major driver of insect declines. Most studies identified agricultural pesticide and fertilizer application as the primary factor driving insect population declines. In intensive agriculture, insecticides, herbicides, and fungicides are used to control pests, competing plants, and fungal infections, respectively. Synthetic fertilizers impact terrestrial plant diversity and pollinator populations, while its runoff contributes to aquatic eutrophication. Research has shown that farm operations apply far more fertilizer than is necessary and there are adverse ecological and human health consequences of these excesses.
While the trends in insect declines are alarming, shining such a bright light on the issue has brought much needed attention. There is reason to be encouraged. The solutions to the problem are evident and include participation from all of us – from the industrial-scale farmer in the Midwest to the urban dweller in the big city.
At the industrial level, the authors note that a rethinking of agricultural practices coupled with habitat restoration is probably the most effective way to prevent further insect declines. For example, a massive reduction in fertilizers and pesticides, addition of grassland and wildflower strips to the edge of crop fields, and rotation of crops that include species that support pollinators are ecological engineering techniques that can actually increase both crop yields and biodiversity.
The European Union has acknowledged the severity of the decline in pollinators. In 2018, the Commission adopted an initiative which aims to 1) improve knowledge of the declines by identifying its causes and consequences, 2) tackle the causes, and 3) raise awareness, engage society-at-large, and promote collaboration.
There has been movement towards integrating natural habitat into the urban jungle. Chicago recently revealed plans for an eco-park along the North Branch of the Chicago River. The project aims to clean up the North Branch, reduce incoming pollution, create wildlife habitat, and promote biodiversity.
At the personal level, we can build on these larger initiatives by incorporating native plants favorable to pollinators in our gardens and on our porches and minimizing fertilizer and pesticide use on our lawns.
At the neighborhood scale, home gardens combined with community gardens create somewhat connected urban pollinator habitat, or hotspots, that can brighten your city block and support healthy insect populations.