An estimated 550 million birds have been lost in Europe over the last 40 years with human use of man-made farm tools largely to blame.
A trickle of studies warning that the enormous variety of living things on Earth is diminishing has turned into a flood. The evidence for these losses within regions and globally is undeniable. But data on biodiversity, and what is causing its decline, is still patchy – restricted to some causes, some places and some species. That isn’t the case for birds in Europe, however.
Birds have long fascinated amateur and professional scientists, and close cooperation across Europe has created a deep body of knowledge about their habits, needs and numbers. Some of the longest-running datasets of their kind concern birds which live at least part of their lives in Europe.
This data paints a grim picture: an estimated 550 million birds have been lost from Europe’s total population over the last 40 years or so. It is a shocking statistic, and tells us something profound about humanity’s broken relationship with nature.
Scientists know that biodiversity is under increasing pressure, especially from rapid changes in how land is used (from forest to farmland, for instance) and rising temperatures. But how different species respond to those pressures, which of them is the most important, and how conservationists can respond to alleviate them, have all remained contentious issues.
Taking advantage of high-quality data on birds, a new paper researchers analysed how 170 bird species have responded to human-induced pressures in Europe, using data collected at more than 20,000 monitoring sites across 28 countries over 37 years, including data from the UK.
We found that chemicals used on farms to control insects and plants seen as weeds that might reduce crop yields are depriving many birds of their main food source, and that this is the single biggest cause of their decline across Europe.
The four major sources of pressure on bird populations: agricultural intensification (measured by the high use of pesticides and fertilizers), climate change and its influence on temperatures, changes in forest cover, and urbanization.
Modern farming methods were the biggest cause of decline for most bird populations – especially for those that feed on insects and other invertebrates, such as swifts, yellow wagtails, spotted flycatchers, wheatears and stonechats. How birds responded to changes in forest cover, urbanisation and climate change was much more variable and species-specific.
Between 1980 and 2016, common birds in Europe declined in abundance by a quarter. But numbers of farmland birds more than halved during this period.