More butterfly species are becoming extinct in northern Belgium than in
any other part of Europe. Urbanization and intensive agriculture are probably
to blame, new research suggests.
Nearly a third of Flanders' 64 native butterfly species have become extinct in the past 100 years; half of those remaining are endangered, report Dirk Maes of the Institute of Nature Conservation in Brussels and Hans Van Dyck of the University of Antwerp, Belgium. At this rate, the endangered butterfly species could disappear in just 65 years, the researchers predict.
More sensitive to environmental changes than other organisms, butterflies are considered the 'canary in the coal mine' - an early warning of habitat deterioration and its impending impact on other organisms. Butterflies are threatened elsewhere in the world, but censuses have generally been conducted in Western Europe, because smaller geographical areas make counting easier.
"Flanders may look green to a visitor, but most habitats are seriously affected by intensive agricultural practices," says Maes. One of the most densely populated regions in Europe, Flanders' explosion of roads and housing has eroded surrounding natural habitats and kept nature reserves among the smallest in Europe.
Furthermore, manure for Flanders' high-production agriculture introduces some of Europe's highest levels of nitrogen into the environment. The European Union recently warned Belgium that it was applying too much nitrogen to its soils.
Nitrogen causes excessive grass growth in meadows where many butterflies live. The added shade cools the ground, killing caterpillars adapted to warmer climates.
"The authors build an extremely strong case showing the effects of land-use changes on biodiversity loss," says butterfly expert Carol Boggs, director of the Center for Conservation Biology at Stanford University in California. "The impacts are becoming more pervasive across the landscape."
Nature reserves may also be at fault. Many reserves are shrinking and are managed with only plants, birds and mammals in mind. They don't account for the needs of butterflies, says Maes. For example, cattle in one reserve were grazing on plants that one species of butterfly called home, with the result that the butterfly became extinct.
Maes and Van Dyck took advantage of Europe's long history of amateur butterfly-watching. They compared nineteenth-century records with modern-day field observations. Unfortunately, the lack of high-speed transportation in the nineteenth century limited the area over which amateurs regularly observed butterflies. The researchers were therefore also limited to data from only 23% of Flanders.
Early analyses of more detailed field data collected throughout Flanders during the past decade lead Maes and Van Dyck to suspect that they have underestimated the butterfly loss. For example, they thought that the population of Maculinea alcon, the most endangered butterfly in Flanders, had declined by about 70%. They now put the figure closer to 90%.
Maes and his colleagues have drafted an action plan for M. alcon. It calls for the enlargement of the butterfly's habitats and the cutting back of plants that compete with those on which butterflies and caterpillars live.