Thursday, July 30, 2009

Human activity causing mass extinction

Human activity is driving Earth's 'sixth great extinction event'
The Guardian: Earth is experiencing its 'sixth great extinction event' with disease and human activity taking a devastating toll on vulnerable species, according to a major review... [The] report identifies six causes driving species to extinction, almost all linked in some way to human activity... Species are being threatened by habitat loss and degradation, invasive species, climate change, over-exploitation, pollution and wildlife disease...

The report sets out a raft of recommendations to slow the decline by introducing laws to limit land clearing, logging and mining; restricting deliberate introduction of invasive species; reducing carbon emissions and pollution; and limiting fisheries. It raises particular concerns about bottom trawling, and the use of cyanide and dynamite, and calls for early-warning systems to pick up diseases in the wild.

Dead and buried

Cretaceous-Tertiary: 65m years ago the dinosaurs were wiped out in a mass extinction that killed nearly a fifth of land vertebrate families, 16% of marine families and nearly half of all marine mammals. Thought to have been caused by asteroid impact that created Chicxulub crater in the Yucatan.

End of Triassic: About 200m years ago, lava floods erupting from the central Atlantic are thought to have created lethal global warming, killing off more than a fifth of all marine families and half of marine genera.

Permian-Triassic: The worst mass extinction took place 250m years ago, killing 95% of all species. Experts disagree on the cause.

Late Devonian: About 360m years ago, a fifth of marine families were wiped out, alongside more than half of all marine genera. Cause unknown.

Ordovician-Silurian: About 440m years ago, a quarter of all marine families were wiped out by fluctuating sea levels as glaciers formed and melted again.
Image source here.