Hundreds of species likely to go extinct in the next few decades
By Summit Voice
SUMMIT COUNTY — Global warming is likely to drive hundreds of bird species to extinction in coming decades, as more intense and frequent extreme weather events destroy habitat and make foraging impossible.
“Birds are perfect canaries in the coal mine – it’s hard to avoid that metaphor – for showing the effects of global change on the world’s ecosystems and the people who depend on those ecosystems,” said Çağan Şekercioğlu , an assistant professor of biology at the University of Utah.
Şekercioğlu recently reviewed 200 scientific studies on climate change impacts to birds, concluding that 600 to 900 species are likely to go extinct by 2100. For context, there area about 10,000 bird species worldwide. The research suggests that each degree of warming could lead to the extinction of an additional 100 to 500 species.
About 87 percent spend at least some time in the tropics, but if migratory birds are excluded, about 6,100 bird species live only in the tropics, according to Şekercioğlu.
About 12.5 percent of the world’s 10,000 bird species are already threatened with extinction – listed as vulnerable, endangered or critically endangered by the International Union for Conservation of Nature.
“The balance of evidence points to increases in the numbers of intense tropical hurricanes (though hurricane frequency could decrease overall),” Şekercioğlu and colleagues write. “This would predominantly affect tropical bird communities, especially species living in coastal and island habitats.”
Şekercioğlu said it is difficult to predict how habitat loss, emerging diseases, invasive species, hunting and pollution will combine with climate change to threaten tropical birds; what is known is that habitat loss [from agriculture and development] can increase bird extinctions caused by climate change by nearly 50 percent, he explained.
The researchers suggests that:
- Climate change already has caused some low-elevation birds to shift their ranges, either poleward or to higher elevations, causing problems for other species. Global warming helped rainbow-billed toucans move from Costa Rican lowlands to higher-elevation cloud forests, where they now compete for tree-cavity nest space with the resplendent quetzal. The toucans also eat quetzal eggs and nestlings.
- Birds with slower metabolisms often live in cooler tropical environments with relatively little temperature variation. They can withstand a narrower range of temperature and are more vulnerable to climate change.
- Climate change may spread malaria-bearing mosquitoes to higher elevations in places like Hawaii, where the malaria parasite can threaten previously unexposed birds.
- Longer and less regular dry seasons and droughts expected during global warming may reduce populations of tropical birds that often time their breeding with wet seasons when food is abundant.
Şekercioğlu acknowledged that “not all effects of climate change are negative, and changes in temperature and precipitation regimes will benefit some species … Nevertheless, climate change will not benefit many species.”
A 2008 study by Şekercioğlu and climatologist Stephen Schneider calculated 60 scenarios of how tropical land bird extinction rates will be affected by various possible combinations of three variables: Climate change, habitat loss and how easily birds can shift their range, moving to new habitat.
- Tropical mountain birds are among the most vulnerable to climate change. Warmer temperatures at lower elevations force them to higher elevations where there is less or no habitat, so some highland species may go extinct.
- Climate change and accompanying sea-level rise pose problems for birds in tropical coastal and island ecosystems, “which are disappearing at a rapid rate,” Şekercioğlu and colleagues write. Many such ecosystems already have been invaded by non-native species and exploited by humans.
- Birds in extensive lowland forests with few mountains – areas such as the Amazon and Congo basins – may have trouble relocating far or high enough to survive.
- Tropical birds in open habitats such as savanna, grasslands, scrub and desert face shifting and shrinkage of their habitats.
- Rising sea levels will threaten aquatic birds such as waders, ducks and geese, yet they often are hemmed in by cities and farms with no place to go for new habitat.
- Tropical birds in arid zones are assumed to be resilient to hot, dry conditions, yet climate change may test their resilience by drying out oases on which they depend.
To better understand and reduce the impact of climate change on tropical birds, Şekercioğlu urged more research, identification and monitoring of species at greatest risk, restoration of degraded lands, relocation of certain species, and new and expanded protected areas and corridors based on anticipated changes in a species’ range.
“Nevertheless,” Şekercioğlu and colleagues write, “such efforts will be temporary fixes if we fail to achieve important societal change to reduce consumption, to control the emissions of greenhouse gases and to stop climate change.”
“Otherwise,” they add, “we face the prospect of an out-of-control climate that will not only lead to enormous human suffering, but will also trigger the extinction of countless organisms, among which tropical birds will be but a fraction of the total.”
Şekercioğlu worked with Richard Primack, a biologist at Boston University, and Janice Wormworth, a freelance science writer and ecological consultant in Australia.
Wormworth and Şekercioğlu coauthored the 2011 book, “Winged Sentinels: Birds and Climate Change.” The new article is an updated condensation of that book and another 2011 book Şekercioğlu coauthored, “Conservation of Tropical Birds.”
The review was funded by the Christensen Fund – which finances community-based conservation projects – the University of Utah and National Science Foundation.