The insect decline syndrome

Over the last decades, a significant decline of insect biomass and individual numbers has been repeatedly observed. This decline, here denominated as “Insect Decline Syndrome” (IDS), has been intensively discussed in the scientific literature, and in the media. Although some data may have been overinterpreted, some conclusions have been overgeneralized, and regional differences exist, there is no doubt that insect decline is real, far-ranging, and deeply worrying. While enough evidence has accumulated and some causes are undisputable, it is less clear how much each single factor has, does, and will contribute to this negative trend in the past and foreseeable future. We briefly consider the most relevant factors and discuss IDS from a metapopulation perspective, concluding that the current decline might be the consequence of long-term environmental deterioration processes associated with the Anthropocene. We suggest that IDS is a complex, nonlinear and multifactorial, context-dependent phenomenon. While the search for the primarily responsible factors is interesting and required and while more research and rigorous data analysis are certainly needed, this should not distract stakeholders and authorities from urgently taking action now. It is time for dedicated action plans, addressing the major drivers of insect endangerment, to protect and support insects in all habitats and regions, since nothing less than human well-being is at risk when insects are being lost at current rates.