Biodiversity is essential for the wide range of economic activities that our planet needs. Yet, the economic consequences of its global decline are hard to estimate, because most population studies focus on individual species in isolation.

Frederik Noack of the University of British Columbia argues that this misses a central insight about biodiversity: a healthy environment depends not just on individual species, but also on the way they work together to keep our natural environment in balance. One especially important aspect of this is the way that birds help keep crops safe from pests and reduce the need for pesticides.

He tells Tim Phillips about the long-term decline of bird populations in the US and the knock-on effect on agriculture, and pollution.