By Peter Hannam
As if humans weren’t making it hard enough for the world’s creatures great and small.
Evidence continues to mount that global warming is having an impact on ecosystems across the planet in a myriad of ways, altering both individual species and ecological communities.
There’s really nowhere on earth where the natural systems are not being affected by climate change,” Lesley Hughes, a professor of biology at Macquarie University, said.
“Climate change is simply an additional stress on already stressed ecosystems,”
Professor Hughes said, listing habitat loss, pollution and over-exploitation among the existing challenges.
A recent paper in Science said research on 94 core ecological processes and found 82 per cent were already revealing climate change impacts as temperatures warmed.
James Watson, a conservation biologist at the University of Queensland and one of the paper’s authors, said people often fixated on polar bears, penguins or another emblematic species.
They think, ‘that’s miles away from me; it’s a pity but it doesn’t affect me’,” Professor Watson said. “It’s everything that’s affected.”
Here are six key areas of change:
Warming temperatures alter the sex ratio of offspring of certain marine and terrestrial species.
As Fairfax Media reported, sea turtle eggs incubate at a uniform 29 degrees, with the male-female ratio changing according to temperature. If temperatures reach 30.5 degrees all offspring will be females. (Should the species survive long enough without males, 33 degrees is enough to ensure no embryos make it.)
Changes, such as increasing acidity as waters absorb more carbon dioxide.
Corals are among the species in the firing line, as are creatures with shells, such as tiny pteropods, the Science paper said.
“Severe levels of shell dissolution” were reported for some Antarctic pteropods, according to a paper in Nature Geoscience.
“As deep-water up-welling and CO2 absorption by surface waters is likely to increase as a result of human activities, we conclude that upper ocean regions where aragonite-shelled organisms are affected by dissolution are likely to expand,” the paper said.
These kinds of changes “have the capacity to undermine and change dramatically the structure of marine food webs, which ultimately underpin much of the protein sources for humans”, Professor Hughes said.
Species with short generation spans, such as phytoplankton, are changing fast, but not fast enough.
In the Gulf of Cariaco, off Venezuela, phytoplankton have managed to adjust their ecological thermal niche by 0.45 degrees over a 15-year period. The response, though, lagged the 0.73-degree warming of waters over that time.
For others, such as the southern flying squirrels on North America, hybridisation with “cousin species” the northern flying squirrel is one response.
Since 1995, a series of unusually warm winters has marked the start of a northward surge of 240 km in the range of the southern squirrel, the Daily Climate reported, based on work published in Global Change Biology.
Similar hybridisation is evident elsewhere, generating other concerns.
“The interbreeding has several consequences, none well understood: It could increase genetic diversity, helping species weather rapid ecosystem changes,” the Daily Climate said. “It also could dilute the genetics of at-risk animals such as polar bears, perhaps even diluting them beyond recognition. And the changes threaten to wreak havoc with conservation efforts.”
Individuals of some species are shrinking in size, as scientists have expected, as creatures with larger surface-to-volume ratios are favoured as temperatures rise.
The body size of six woodland salamander species in the US Appalachian Mountains has shrunk an average of 8 per cent over the past 50 years, Science said.
Also changing colour, other studies showed, with some becoming darker or lighter, depending on local advantages.
The skull shape of alpine chipmunk has “revealed significant changes” in California over the past century as its ranges narrow and its diet changes.
The timing of many life processes of species – such as the budding of plants, the hatching of birds and migration timings – is closely tied to climate variation. Climate shifts are throwing such processes out of whack.
“Across marine, freshwater, and terrestrial ecosystems, spring phenologies have advanced by 2.3 to 5.1 days per decade, the Science paper said. “A combination of climate warming and higher atmospheric CO2 concentrations has extended the growing period of many plant populations.”
Examples include reduced fledging success of tawny owls in the UK as hatchings over the past 27 years have become synchronous with its principal prey, the field vole.
Another predator-prey mismatch is evident among blooms of spring diatoms, which have advanced more than 20 days since 1962, triggering declining populations of its main grazer, the water flea.
A shift in species’ location is one of the most rapid responses observed especially for marine creatures with fewer connectivity issues compared with land-based ones, Science said.
Professor Watson said changing seasonal rains mean Australia’s savannah regions are experiencing more intense fires later in the season, killing off grasses. The result is that rainforests are expanding to fill the ecological gap.
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