Bering Strait: humans not responsible
Permalink: Bering Strait: humans not responsible
A recent report highlights an important claim - that environmental change was primarily responsible for the extinctions of megafauna from the Ice Ages.
Previously, some researchers had tried blaming very small numbers of humans for wiping out entire species, simply by the killing of a few choice animals from any population.
A reflection on the modern relationship between humans and animals, should have clearly wiped out any suggestion that the meagre post-Ice Age human population, could have been responsible for collapsing such extensive populations. After all, humans have been hunting for thousands of years, but had yet to make a point to decimate common and widespread megafauna until the industrialisation of Europe.
Climate - not early human hunters - may have caused the crash in bison populations and the extinction of other big mammals at the end of the last ice age, suggests a new study.
An analysis of the genetic diversity of bison shows that the decline in Beringia - the prehistoric land mass joining Alaska and Siberia - began 37,000 years ago, more than 20,000 years before large human populations reached the area.
And the bison were lucky they did not go extinct as the ice sheets melted about 10,000 years ago, unlike other ice-age megafauna such as sabre-toothed cats.
It is a “big surprise” that the decline began long before people arrived, says Alan Cooper at Oxford University, UK, a member of the international research team. He had thought early North Americans wiped out the megafauna, much like human settlers are believed to have devastated the flightless moa of New Zealand.
Red List increases
Permalink: Red List increases
It’s that time of year, when a few dedicated individuals and organisations sit down and work out how much qorse things have gotten since the previous year.
Coming under the direction of the IUCN - the World Conservation Union - the 2004 Red List of Threatened Species managed to increase the list of threatened species by over 3000 species on the previous 2003 list., resulting in a threatened species list of 15,568 species facing extinction.
This included such tragedies as half the freshwater fish species native only to Madagascar becoming endangered by the diversion of rivers for domestic drinking water projects.
One in three amphibians and almost half of all freshwater turtles are now threatened, as well as one in eight birds and a quarter of known mammals.
For the first time, the Red List includes an index that shows the overall change in threatened status and the projected risk of extinction for each particular species group. The conclusion is that there is an even greater sense of urgency, says Simon Stuart at Conservation International, Washington DC, US.
More information here: Rise in threatened species is accelerating
Moas wiped out before man?
Permalink: Moas wiped out before man?
An interesting study by researchers at the University of Canterbury in Christchurch and the US Forest Service in Missoula, Montana, suggest that humans may not actually have been primarily responsible for the extinction of the Moa bird populations in New Zealand (Aotorea).
Skeletal remains and other clues had previously put the moa population in New Zealand at around 159,000 at the time humans arrived, one thousand years ago. However, after mitochondrial analysis of more than 58 Dinornis remains:
By taking into account other factors that influence genetic variation, such as estimates of the rate at which moa DNA mutates, the Gemmell team calculated that between 300 000 and 1.4 million Dinornis lived in New Zealand between one and six thousand years ago.
From fossil evidence indicating what proportion of the moa population is of the species Dinornis, the researchers obtained an estimate of between 3 and 12 million for all moa species.
That means that if the contentious estimations hold true over a sustained period, then we’re looking at a major crash in Moa populations before humans finally landed and finished them off.
Although the researchers try to suggest disease, it’s hard not to consider an environmental role somewhere.