Agricultural intensification and climate change are rapidly decreasing insect biodiversity

Abstract

Major declines in insect biomass and diversity, reviewed here, have become obvious and well documented since the end of World War II. Here, we conclude that the spread and intensification of agriculture during the past half century is directly related to these losses. In addition, many areas, including tropical mountains, are suffering serious losses because of climate change as well. Crops currently occupy about 11% of the world's land surface, with active grazing taking place over an additional 30%. The industrialization of agriculture during the second half of the 20th century involved farming on greatly expanded scales, monoculturing, the application of increasing amounts of pesticides and fertilizers, and the elimination of interspersed hedgerows and other wildlife habitat fragments, all practices that are destructive to insect and other biodiversity in and near the fields. Some of the insects that we are destroying, including pollinators and predators of crop pests, are directly beneficial to the crops. In the tropics generally, natural vegetation is being destroyed rapidly and often replaced with export crops such as oil palm and soybeans. To mitigate the effects of the Sixth Mass Extinction event that we have caused and are experiencing now, the following will be necessary: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice that empowers the less wealthy people and nations of the world, where the vast majority of us live, will be necessary.

Keywords: agriculture intensification; biological extinction; climate change; insect loss; sustainable agriculture.

Fig. 1.

Agricultural intensification in the tropics. The scale and intensity of agriculture continues to increase at the expense of grasslands and forests worldwide, with the tropics increasingly impacted. Developing productive monocultures allows us to feed our rapidly growing population but leaves little habitat for pollinators, natural enemies, and other wildlife within the cultivated areas. In any case, it theoretically spares more natural and partly developed habitats. In either case, tropical forests, which likely support more than 70% of the global insect species diversity, are rapidly being lost to agriculture, fuel consumption, logging, and increasingly, fires. (A) Soybean harvest near Tangara da Serra in western Brazil. Image credit: Reuters Pictures/Paulo Whitaker. (B) Oil palm plantation (PT Agriprima Cipta Persada Palm Oil Concession) in Papua, Indonesia. Image credit: Greenpeace/Ulet Ifansasti.