Climate change is wreaking havoc on all walks of life—or wings, if you're a bird.
The National Audubon society, in partnership with BirdLife International, released a wide-ranging report this week detailing the effects of climate change on bird populations worldwide. This probably won't come as a surprise, but climate change is already having a drastic effect on some species of birds, and forward-looking case studies predict things will only get worse.
For instance, the balance of European bird communities is rapidly shifting in favour of species better equipped to handle warmer temperatures, and according to another case study, "substantially" more birds regularly found in Mexico have already been lost than gained.
In other words, there are a hell of a lot of ways that our changing climate is going to kill birds.
Local climates are changing. While some bird species have actually benefitted from climate change, and birds that thrive in warmer climates have increased in abundance, according to one case study "there are three times more birds that are negatively impacted by climate change than are positively affected."
The model is based on the projected change in range that birds are expected to have by the end of the century. The model suggests that "climatic change could dramatically alter species composition across Europe" and, to date, over 400 bird species globally "have undergone range shifts that follow the predicted trajectory associated with climate change," according to unpublished BirdLife data.
There is also "compelling evidence" that climate change is sending birds towards the poles, but birds aren't moving north as fast as the climate is changing.
Sea levels are rising—and given the number of species that live just mere meters above sea level, a rise in sea levels is expected to severely impact various species of birds living in low-lying coastal and intertidal habitats. Rising tides cause flooding and erosion, and push high water marks further inland, making small islands, reefs and atolls most vulnerable to sea level rise.
The Australian Department of the Environment and Water Resources, for example, singled out the critically endangered orange-bellied parrot (Neophema chrysogaster), "for which more than 40 percent of their breeding range is in coastal areas beneath 10m elevation."
The cause: warming temperatures cause water to expand—a process known as thermal expansion—and this expansion is "exacerbated by an influx of meltwater from glaciers and polar ice fields" according to one of the case studies in the report. Worse, the rate of sea level rise is accelerating, and current research pegs sea level rise at 0.003m per year, up from an average of 0.002m a century prior.
Food shortages. In the high Arctic, "climate change has caused mismatches between timing of breeding and peak food availability," according to BirdLife International. In other words, temperature changes could mean that food is not most available when young birds need it most. Meanwhile, a reduction in sea ice is thought to have caused declines in krill density of up to 80 percent—a food on which Adélie and Chinstrap penguins both rely.
More predators. In the Czech Republic, higher temperatures have pushed egg laying dates for some species further into the spring, when there are higher populations of edible dormouse than earlier in the season. That's great for the mice, who feed on the nests of local woodland birds, but obviously not so great for the birds.
Extreme weather events. Climate models predict more unpredictable and extreme weather events in future, which will naturally wreak havoc on human and bird populations alike. These rare but high magnitude events "are thought to particularly impact seabirds, through changes in frequency and severity of rainfall, onshore wind and snow storms," and make nests in rocky outcrops more vulnerable to destruction.
Disease. We already know a temperature rise of 2º celsius puts us on the road to a certifiable doomsday scenario for Earth's climate, but here's yet another example of why. Higher temperatures in the Hawaiian Islands will increase the number of low lying mosquitos that transmit avian pox and malaria, a chief killer of native birds. "For example, a temperature increase of 2ºC will almost eliminate low malaria-risk forest in the Hakalau Wildlife Refuge on Hawaii (an important area for five threatened bird species)," one case study reads.
Sure, some of the Hawaiian Islands' 18 threatened bird species could just move higher, but there's only so high they can go; in some areas, higher elevation forests have already been cleared for pasture, limiting upward shifts.
People. Climate change is already having a demonstrable impact on bird populations and habitat ranges. Add in ongoing large-scale deforestation, and you amplify the loss of area and population. "As deforestation is expected to continue," reads one case study, "the ability of endemic birds to adapt to the added pressure of climate change will diminish.
Meanwhile, the production of biofuels—fuels derived from plants such as sugarcane, rapeseed, soya bean and palm oil—is rapidly expanding, but that expansion comes at the cost of forest ecosystems and bird habitats. One cited study found that a newly established oil palm plantation reduced the diversity of bird species by 77 percent.
It's not all doom and gloom, however. A portion of the Audubon Society's report is dedicated to potential solutions that might mitigate some of these problems. It's a start—but there's only so much we can do to reverse the damage that's already been done.