What is happening to insect numbers, and what does it mean?

Reports of declines in abundance of a number of insect species have been increasing over the last two decades. These have variously been attributed to climate change, urbanisation, deforestation, agricultural intensification, habitat fragmentation and pesticide usage. The picture has been complicated by the fact that not all insect groups have shown the drastic declines reported for others, flawed methodology, paucity of long-term studies, the lack of data from the tropics with most long-term studies emanating from Europe and North America. In addition, the number of insect groups studied has largely been restricted to charismatic species such as Hymenoptera, Lepidoptera, Coleoptera and Odonata. Despite this, the evidence for long-term declines in insect abundance is incontrovertible. To aid in our understanding of the problem we need to set up more globally coordinated studies, use past data in innovative ways and convince policy makers and governments to support these studies.