Global Change Biogeography: November 2011

Wednesday, 9 November 2011

Biological responses to climate change II- Extinctions

Despite it is extremely hard to attribute a single cause to an extinction event, there are documented cases of climate change induced extinctions. For example in spite of habitat protection, 67% of the cloud forest specialist South American harlequin frogs (genus Atelopus) already went extinct and many more are critically endangered (see IUCN red list). Interestingly despite these are mountain restricted species, the reason for their extinction is not the loss of habitable climatic space, as we may think. Instead, altered dynamics of the Chytridiomycosis disease caused by the fungus Batrachochytrium is responsible for the mass decline of these species. Pound and colleagues (2006) showed that the increased cloudiness resulting from warming shields the forest from heat, and provides the moist conditions required for the survival, growth and reproduction of Batrachochytrium. This example reminds me again how complex the earth-system and ecosystems are. Higher temperature causes increased evaporation which in turn results in more clouds. Clouds reflect sunlight, protect from too high temperatures and aids the reproduction of a fungus, which after penetrating the frog's skin completes it's life cycle and kills the frog. How many similar pathways exist, and what small fraction of these will ever be discovered? Staggering....

Thursday, 3 November 2011

Biological Responses to Climate Change I - Range Shifts

Climate change is probably the most widely discussed global environmental issue of our day. When I carried out a small survey for a project with my friend and asked people on the street to list the global environmental issues they are aware of, nearly everyone mentioned climate change on the first place and only a few noted pollution, biodiversity loss, deforestation or any other issues. Things are no different in the media: if one looks at Richard Black’s Environment blog on BBC, they will find that a great proportion of entries are on climate change and less attention is payed to other environmental problems. Therefore I will start the blog by discussing the biological effect of climate change.

Conservation News

Ocean Acidification
It is a well known fact that increased acidity of oceans prevents coral growth, but new studies suggest that it also jeopardise fish reproduction. Science news reports on two studies, which showed that survival of young fish and hantching success of newly fertilized eggs decreased dramatically with higher acidity. In one study, CO2 levels as high as 1000ppm, which may be reached by 2100, decreased silverside egg survival from around 50% (at current CO2 elvels) to only 10%. The other study looked juvenillye cod growth in acidic water, and found that despite cods grew faster, they matured later and suffered higher mortality. If these findings hold true for other fishs species as well, it could mean that fish populations, both with commercial and conservation importance are doomed by increasing CO2 emissions.

Starving Polar Bears Cannibalise Cubs
Due to melting sea ice, polar bears are trapped on shore and are exposed to extended period of starvation. Lacking other alternative, they sometimes cannibalise juveniles. Such incidents become more and more frequent, and now for the first time one has been photographed. The issue of starving polar bears is also covered in the final episode of the Frozen Planet series (see blogpost).

Black Rhinos Declared Extinct
Remainig unrecorded for the past six years, black rhino (Diceros bicornis) was declared extinct by IUCN. It's highly valued horn in chinese medicine, slow life history, and a generally poor law enforcement throughout it's range in West Africa are thought to be the main drivers of it's decline and extinction. R.I.P.

White Nose Syndrome
Earlyer this year, Science news reported on the 'worst wildlife disease of recorded history', an alien fungus caused epidemic that kills tens of thousands of bats in North America. Interestingly, while Geomyces destructans leaves european bats unaffected, it causes 'white-nose syndrome' in the USA and Canada, and have devastating effect. Recent findings suggest that despite the process is long, recovery may be possible.