The Earth has a fever
The effects of global warming, the planet's ecosystems are no longer just predictions related to future scenarios, but are already in place, and at every level of the biosphere. The confirmation comes from a group of experts, including a dozen biologists, ecologists and botanists of American, English, French, German and Australian, who has reviewed the main studies, about one hundred, on ecological processes sensitive to climatic change. The results of this analysis were published in the journal Nature, in the March issue, and are not very encouraging. The increase of 0.6 degrees in average temperatures recorded in the last century, Earth has in fact influenced the phenology and physiology of organisms, the diversity and geographical distribution of species, and the length of the seasons.
E 'perhaps the most recognizable of the latter precisely because mutations in the sight of all. Spring arrives earlier in 1960, increasing its duration of about 12 days: the return of migratory birds, the appearance of butterflies, the flowering of the trees, everything comes early, stimulated by the mild climate. The risk, however, that sudden drops in temperature or sudden frost undermine the new buds or freshly laid eggs. In contrast, the temperature increase delays the arrival of autumn, from a minimum of 0.6 to a maximum of 3.6 days per decade. But this trend is less pronounced and even contradictory.
Climate change has also changed the distribution of species: the warming has in fact led to the transfer of habitats to high latitudes. Bodies at this point are only two ways to survive or adapt to new conditions move in search of more favorable locations. For species that are unable to keep up with events there is only the extinction. And 'what is happening to corals that are at lower latitudes the lighting conditions in the tropics and the equator. In this way, has already lost 27 percent of the reefs on the planet.
Neither the massive migration of species into new habit can be said without risk, the risk of altering the balance of pre-existing ecosystem is strong. The recent invasion of the Mediterranean by tropical fish and seaweed, for example, has affected many native species, and colonization by Antarctic mosses and invertebrates has contaminated an ecological niche remained until a few years ago, totally isolated from the rest of planet.
accurate and reliable indicators of climate change are amphibians and reptiles. Their cold-blooded as they are extremely dependent on temperature and humidity. In some species turtle sex of offspring is related to temperature in July: a modest increase (2-4 degrees) is sufficient to reduce the number of male members of the group. For some species, climate change has proved a source of risk indirect warming of the waters of the Southern Ocean has dealt a blow to the production areas of krill, the main food of whales, seals, penguins and seabirds. As early migrations have brought some species to compete for food resources available and not enough to cover this unexpected surplus of predators.
There are many mechanisms that researchers have yet to be clarified. "The complexity of ecological interactions renders difficile estrapolare i dati dagli studi" scrivono gli autori.Questo perché per le indagini ecologiche si lavora su scala locale e a breve temine (alcune decadi), mentre la climatologia utilizza scale spaziali e temporali più ampie. Tuttavia già questi primi dati spingono a riflettere: se variazioni climatiche tutto sommato piccole hanno determinato implicazioni di così vasta portata, che cosa accadrà nei prossimi anni in cui si prevedono aumenti di temperatura sempre più consistenti?
Marina Caporlingua
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