|Year||All common birds (168 species)||Common farmland birds (39 species)||Common forest birds (34 species)|
The status of birds and butterflies has been the subject of long-term monitoring in Europe, much of it via voluntary effort, and is a good example of how the power of citizen science can be released through effective targeting. Both species groups are sensitive to environmental change and their population numbers can reflect changes in ecosystems and other animal and plant populations. Therefore, trends in bird and butterfly populations can serve as barometers of the health of the environment and can help measure progress towards biodiversity targets.
Long-term monitoring of common birds in 25 EU Member States reveals significant population declines, particularly in farmland birds, with no signs of recovery. Between 1990 and 2019, the common bird index declined by 8%; the decline in common farmland birds was much more pronounced, at 27%; while the common forest bird index increased by 5%. Although this indicator uses 1990 as a baseline, significant decreases had occurred before this date.
The long-term trends demonstrate a major decline in biodiversity in Europe. This has been caused primarily by the loss, fragmentation and degradation of natural and semi-natural ecosystems, mainly due to agricultural intensification, intensive forest management and land abandonment or urban sprawl. Habitat loss, fragmentation and simplification (e.g. removal of hedgerows and tree lines to make fields larger) result in loss of bird nesting sites and food sources, contributing to population decline.
Factors that can have adverse effects on the recovery of populations include climate change, intensive agricultural production, urban sprawl and increasing competition for land for production of renewable energy and biofuels.
Measures set out in, for instance, the Birds and Habitats Directives, the Water Framework Directive and the common agricultural policy (CAP) aim to help populations recover at national and European levels. However, achieving the wide and effective deployment of conservation measures remains a challenge.