jueves, 9 de septiembre de 2010
Most Penguin Populations Continue to Decline, Biologists Warn
Penguin biologists from around the world, who are gathered in Boston the week of September 6, warn that ten of the planet's eighteen penguin species have experienced further serious population declines. The effects of climate change, overfishing, chronic oil pollution and predation by introduced mammals are among the major factors cited repeatedly by penguin scientists as contributing to these population drops. Prior to the conference, thirteen of these penguin species were already classified as endangered or threatened. Some penguin species may face extinction in this century.
More than 180 penguin biologists, government officials, conservation advocates, and zoo and aquarium professionals from 22 nations have convened in Boston for the five day International Penguin Conference, which is being hosted this year by the New England Aquarium. The conference is held every three to four years, and this is the first time that it has been held in the Northern Hemisphere.
Penguins are found exclusively in the Southern Hemisphere with a single species on the Galapagos Islands at the Equator to four Antarctic penguin species that are most well known to the public, yet 13 other species also live in South America, southern Africa, Australia, New Zealand, and on the many sub-Antarctic islands. Throughout their ranges, nearly all of penguin species are in significant decline or under duress due to a host of common factors.
Climate Change Concerns
The effects of climate change on different penguin species has been the topic of many of the scientists's papers and presentations. Many penguin species are highly dependent on small schooling fish for food. These masses of anchovies, sardines and other small finfish are seasonally brought to many penguin habitats by cold water currents. In years with El Nino events in the Pacific, there has been a dramatic warming of sea surface temperatures which effectively blocked cold water currents coming up the western coast of South America. Consequently, Galapagos penguins and Humboldt penguins, which are found on the coasts of Peru and Chile, have suffered due to reduced food availability, which principally affects the survival of the young. Galapagos penguins stand a 30% probability of becoming extinct in this century and Humboldt penguins have been classified by the Peruvian government as endangered.
Earlier this year, African penguins, found in Namibia and South Africa, were reclassified internationally as endangered as many breeding colonies in the western part of their range have disappeared. Important food bearing cold water currents have shifted and are now routinely found much further offshore. The increased roundtrip commuting distance for African penguins to obtain food has been devastating to their population.
Scientists are closely watching the potential effects on several Antarctic penguin species that are highly dependent on the presence of sea ice for breeding, foraging and molting. Emperor penguins, which were the subject of "March of the Penguins," could see major population declines by 2100, if they do not adapt, migrate and change the timing of their growth stages.
Adelie penguin colonies in the Antarctic's Ross Sea have coped for several years with two super-sized icebergs that have grounded there and created an enormous physical barrier. It has resulted in lower breeding rates and the migration of many animals out of the area.
Sea ice also creates an important nursey cover for juvenile krill which feed on ice algae. Krill is the primary fuel at the base the Antarctic food chain. Reduced sea ice cover has led to a dramtic decline in krill and will likely lead to a decline in many wildlife populations further up the food chain that relies on krill as its foundation food source.
The effects of climate change on penguins are very real. Many environmental conditions are changing and much less predictable. For penguins living in harsh conditions, the ability to properly time when to migrate, nest, mate and seek food are critical decisions often with a very small margin for error, both for both individual animals and entire species.
Overfishing and Bycatch
As fishing efforts around the globe have multipled several fold over the last few decades, penguins are now competing with people for enough food. The large scale harvesting of anchovy and sardine stocks have directly reduced the prey available to many penguin species including Macaroni and Chinstrap penguins in the South Atlantic. Combined with the effects of climate change on the locations of fish stocks, reduced food availability leads to higher starvation rates, increased vulnerabilty to disease and lower breeding success.
Thousands of penguins are also killed annually when caught in fixed fishing nets.
Large scale oil spills make worlwide headlines, but chronic petroleum pollution has killed thousands of penguins particularly off the coasts of South America and South Africa. The most common sources are illegal operational dumping from ships, long term leaks from sunken ships and some land-based discharges. Better legislation and law enforcement efforts can yield positive results. The incidence of oiling of Magellanic penguins off the coast of Argentina has decline signficantly in recent years due to increased public awareness and enforcement.
Introduced Mammalian Predators
Many penguin species evolved in extremely remote settings devoid of any mammal predators.. Prior to the arrival of humans, New Zealand's only mammals were bats. Now, introduced weasels have had a large impact on the the small populations of Yellow-Eyed and Fiordland penguins. In Australia and Argentina, the arrival of foxes have had impacts while feral cats in the Galapagos have reduced penguin populations there.
The goal of the 7th International Penguin Conference is to present ongoing research, identify current and emerging conservations issues and create action plans that will help create a strategic global effort on behalf of these threatened species.