Media releaseFrom: PNAS
Global decline of insects
With more than a million described species and a history of terrestrial abundance dating back more than 400 million years, insects might appear as a group to be indestructible, but recent studies documenting striking patterns of decline have raised concerns about their future in a world profoundly altered by human activities. The 12 papers in the Global Decline of Insects in the Anthropocene Special Feature examine losses of insect biodiversity from multiple perspectives. The 56 authors evaluate threats to insect biodiversity across three main dimensions of declines—insect biomass, abundance, and species numbers. Many insect populations are decreasing at annual rates of 1-2% a year—a dangerous clip when extended over even a few decades. In a perspective Raven and Wagner place these declines in the context of human population growth, currently at 7.8 billion and already exploiting most of the planet’s arable land for agriculture. Two articles document worrying declines of butterflies and moths in the Neotropics, both linked to climate changes and harbingers of the broader fate of Earth’s tropical forests, home to the vast majority of insect species. At the same time, several papers identify species that are increasing in abundance and geographic distribution, especially in temperate and Arctic areas, where insects have been historically limited by winter conditions. The collection exposes many of the challenges associated with documenting insect diversity. Schowalter et al., for example, provide new data that contradicts an earlier study of catastrophic losses of insects in a Puerto Rican forest. Janzen and Hallwachs describe an ambitious effort by Costa Rica to bioinventory its entire biota to advance national bioliteracy and the long-term protection of its wild biodiversity. Many of the articles suggest ways forward—short- and long-term actions, ranging from the individual to the national level—to protect insects and sustain the ecosystem services that they provide.