By Sheana Laughlin
20 May 2008 [MediaGlobal]: Birds are regarded as one of the best indicators of biodiversity because they connect and inhabit all ecosystems in the world, making their plummeting numbers of grave concern, the United Nations Environment Programme (UNEP) reported on World Migratory Bird Day last week.
“Migratory birds play a key role as biodiversity indicators,” said Robert Hepworth, Executive Secretary of the Convention on Migratory Species (CMS), in a recent press release. “Any impact on ecosystems resulting from climate change, habitat degradation or availability of prey is reflected in the migration patterns and timing and breeding output of migratory birds.”
Scientists are recording a decline in the numbers of many migratory bird species along all of the globe’s major flyways, the main migration systems and corridors used by birds across the world. For example, 41 percent of the 522 migratory waterbird populations on the African-Eurasian flyways are declining and there are reports that numbers of migratory songbirds using the same flyways are also decreasing, UNEP reported.
“The majority of species have been declining gradually over time,” Sergey Dereliev, Technical Officer at UNEP’s African-Eurasian Waterbird Agreement (AEWA), told MediaGlobal. “There are, however, examples of very rapid crashes of populations, such as the Asian vulture crisis, where over the course of three years 95 percent of birds of three species of vultures were lost in large parts of their range,” he added.
The Steppe Eagle is classified as a long-distance migrant, flying over
a large part of the world from Central Asia, through the Middle East and
down to South Africa. During its long journey it depends on many different
ecosystems as stopover sites. (Source: Sergey Dereliev, UNEP/AEWA)
The exact reasons for the global decline are complex and vary from species to species, but UNEP states that the drop in numbers is indicative of larger environmental problems linked to the loss of biodiversity worldwide.
“There are many types of pressures, which have negative impacts which are affecting bird populations gradually or rapidly. Habitat loss is of greatest significance and is being aggravated by climate change, but other human-induced factors are playing a significant role as well.” Dereliev said.
Many populations are being over-harvested for consumption and trade. Others, such as the albatross, are accidentally caught by fishing boats or collide with man-made structures such as wind farms, power lines and tall buildings, he added.
Migratory birds, particularly long-distance migrants, are most vulnerable to environmental changes. “To complete their annual migrations, they require breeding and wintering areas but also a network of stop-over sites along their flyways where they can rest and refuel before continuing on their journeys,” UNEP notes.
But these essential sites, which also host other threatened plants and animals, are on a global decline, largely due to agriculture, urban growth, and infrastructure and industrial development. For migratory birds, this means the network of sites they depend on to complete their annual journeys is getting sparser.Furthermore, the loss of habitats is compounded by the effects of climate change. “Rising global temperatures lead to expanding deserts and more frequent storms which impact bird migration, and subsequent sea-level rise threatens tidal and wetland areas which are important for many migratory birds – all factors scientists are also linking to their decline,” UNEP reported.
Experts stress that the global drop in bird numbers is a is a clear signal to world leaders that more needs to be done to stop the loss of biodiversity and to increase international efforts to preserve the network of habitats required by migratory birds.
According to Birdlife International, it is still possible to reverse the trend. “But this requires a multitude of approaches, tackling species-specific issues such as unsustainable [and/or] illegal hunting, ensuring effective management of critical sites along migration flyways as a whole, and addressing human-induced changes to migratory bird habitats,” the organization told MediaGlobal through email correspondence.
International collaboration is key to producing results, and these approaches are part of the work of Birdlife partners at national levels, Birdlife International said, adding that efforts to conserve migratory birds in one part of the world may be wasted if they are being killed and their habitats destroyed elsewhere.
It is important to remember that humans depend on the same environmental elements and ecosystems as birds, Dereliev said.
“If we compare an ecosystem with a flying airplane, then losing species would be like losing bolts and critical pieces in mid-air, causing the plane to crash. Depleted ecosystems are much [more likely] to fall apart and will stop providing the services, which also humans depend on and take for granted, like food, air and water,” he added.