Sunday, 19 February 2012

All of a Flutter in the Tropics

"Global warming threatens tropical birds" says Bob Berwyn, who's editor and apparently the only "journalist" on the Summit County Voice.
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.
Other sites used identical wording, with more or less detail, suggesting a press release, which none cited, or the version on EurekAlert, which is the most detailed:
Scenarios for Extinction
A 2008 study by Şekercioğlu and late 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, meaning move to new habitat. Citing those estimates, the new review paper says that "depending on the amount of habitat loss, each degree of surface warming can lead to approximately 100 to 500 additional bird extinctions."
The Intergovernmental Panel on Climate Change has predicted 1.1 to 6.4 degrees Celsius (2 to 11.5 degrees Fahrenheit) of global warming of the Earth's surface by the year 2100, which Şekercioğlu's study converted into a best case of about 100 land bird extinctions and a worst case of 2,500.
He says the most likely case now is considered to be 3.5 C (6.3 F) warming by 2100, resulting in about 600 to 900 land bird species going extinct. These estimates are conservative because they exclude water birds, which are 14 percent of all bird species.
Because they don't travel far, "sedentary" birds "are five times more likely to go extinct in the 21st century than are long-distance migratory birds," says Şekercioğlu.
My first observation is that the cited Intergovernmental Panel on Climate Change (IPCC) also predicted that warming would be less in the tropics, so any climate modelling based on the tropics should take that into account. Apparently this modelling exercise (for that, of course, is what it is) did not, a significant error. I suggest you read the EurekAlert article, if you're interested in doom and gloom. My second observation is that these and many other articles equate "global warming" and "climate change", and use them interchangeably. They are not the same thing. Climate consists of a lot more than temperature.

I responded to Mr. Berwyn's article before I'd spotted the error with "projected" temperature increases, quoting and commenting on the article thus:
"Climate change already has caused some low-elevation birds to shift their ranges, either poleward or to higher elevations, causing problems for other species"
Wouldn't the "other species" have moved "either poleward or to higher elevations" also? Birds and other species have been moving poleward and to higher elevations since the end of the last ice age.
"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"
So? This paper says explicitly that birds relocate to suit the conditions. There's nothing to suggest the "cooler tropical environments" wouldn't move poleward somewhat and the birds with them, nor that the "little temperature variation" would alter.
"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"
We're frequently told that plants, including trees, are moving higher with increasing temperatures. I would equate "plants, including trees" and suitable temperatures with habitat.
"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"
What rapid rate? What island ecosystems?
"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"
Birds worldwide migrate thousands of miles each year but can't manage to move their nesting sites a few miles a decade?
"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"
Most aquatic birds nest and feed far away from cities and farms. There aren't many of either on estuary mudflats. cliffs and rocky islands.
"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"

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