Tuesday, April 16, 2013

Delayed extinction

Earth went through several larger extinction events. They were perhaps caused by meteorite impacts, increased volcanic activity or other major shifts of environmental conditions. In light of the current rate of species loss many experts are referring to the sixth major extinction event in Earth's history. But this time the main causes are related human activities and the main ones are pollution, habitat loss and fragmentation, and the spread of invasive species.

In order to better understand present species extinction a group of researchers related numbers of threatened species appearing on national red lists to historical and contemporary levels of socioeconomic pressures across 22 European countries. 

Their findings are concerning. Proportions of species facing medium-to-high extinction risks are more closely matched to indicators of socioeconomic pressures (i.e., human population density, per capita gross domestic product, and a measure of land use intensity) from the early or mid-, rather than the late, 20th century.

The researchers conclude that irrespective of recent conservation actions, large-scale risks to biodiversity lag considerably behind contemporary levels of socioeconomic pressures. The negative impact of human activities on current biodiversity will not become fully realized until several decades into the future. Mitigating extinction risks might be an even greater challenge if temporal delays mean many threatened species might already be destined toward extinction.
The current Red List status of plants, dragonflies and grasshoppers is best explained by historical data of the years around 1900. Species are disappearing although causes such as increased use of fertilizer and drainage already reached a peak decades ago. The situation of mammals and reptiles also highly correlates with the first half of the 20th century. Only the decline of fish species could be related to more recent data which could be explained by the immediate and strong impact of pollution and building activities.

Minimizing the magnitude of the sixth extinction crisis might be an even greater challenge when temporal delays are taken into account.

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