miércoles, 9 de julio de 2008

Actualidad: el cambio climático amenaza a las ballenas!

Especies como la yubarta (Megaptera Novaengliae), el rorcual aliblanco (Balaenoptera bonaerensis) o la ballena franca austral (Eubalaena australis) podrían ver menguadas gravemente sus poblaciones debido a un cambio en la temperatura del mar.

Las temperaturas podrían afectar principalmente a la disponibilidad de alimento afectando a toda la cadena trófica.

La noticia:

CLIMATE change could help do to whale populations what commercial whaling has not - wipe out an entire species.

Humpback, southern right and minke whale populations could be damaged by a lack of food caused by a change in sea temperatures, according to researchers from the Federal Environment Department. Data from the department’s Australian Antarctic Division (AAD), published in the Marine and Freshwater Research journal, claimed that if the availability of krill - the main diet for “baleen” whales which filter food from water - deteriorated due to climate change, other species could be wiped out. “In an era of climate change, the ecological effects of baleen whales, and the effects of physical changes on these key predators can no longer be ignored,” the researchers said. “The abundance of their primary prey, krill, can vary dramatically over relatively short periods of time and baleen whales that feed on krill have adapted to this variability. “However, if climate change causes monotonic shifts in either krill distribution and/or abundance, then the extent of this adaptability in the longer term… is largely unknown but could impact reproductive success and ultimately survival.” Krill is a small shrimp-like animal that is a main source of food for whales, seals and other animals.

Melting ice

According to report co-author, AAD researcher Dr Anthony Worby, if ice around Antarctica melts as predicted, krill would lose its natural habit and struggle to survive. “Because krill is one of the fundamental parts of the Southern Ocean ecosystem, on which whales and penguins and seals and seabirds all feed… obviously there’s growing interest in (its) reproductive patterns,” Dr Worby, a sea ice physicist, told NEWS.com.au. Director of Southern Cross University’s Whale Research Centre, Associate professor Peter Harrison, said he did not believe the melting ice would be “doomsday” for whales. But Dr Harrison also said the entire food chain in the Southern Ocean would be a significant factor in stopping whale populations to recover from whaling. “It is very clear that there is a significant risk to cetacean species,” Dr Harrison said. CSIRO marine biologist Dr Elvira Poloczanska said the risk of whales dying because of climate change was “a valid concern”. “I’m not quite sure there’s much more (alternative foods) available for whales in the Southern Ocean,” Dr Poloczanska said.

Matter of urgency According to the research, the full extent of future damage to whales may not be known for many years – but it was a matter of urgency to find out before it was too late. “If the sea ice environment changes in future and if this is associated with changes in oceanic circulation, then this will undoubtedly affect the ecosystems on which predators such as baleen whales depend," the researchers said. “Given the strong link between ice-edge retreat and productivity in the Southern Ocean, these effects are unlikely to be benign, however, the magnitude and type of any change is currently difficult to predict. “Understanding the changes occurring in Southern Ocean ecosystems will require concerted integrated studies in the future, and not a little ingenuity.”