Update: climate change can cause extinction

Have a look at this article on the bitsofscience website. An interesting update to the earlier post about 'mass extinction', this article mentions the Permian and other mass extinctions linked to climatic changes, but it seems that there is more certainty that past climate change was the dominant reason for biodiversity loss for more recent, smaller extinction events. 

European fish species are in a tricky stituation...

The BioFresh project mentioned earlier hosts a blog on the topic of freshwater ecosystems, and their latest post caught my eye. It picks up of the publication of the newest International Union for Conservation of Nature's Red List, which identifies the European species threatened with extinction, and highlights the particularly vulnerable status of Europe's freshwater fishes and lampreys. The Red List has had news coverage by the BBC and Telegraph too. Most interesting in the BioFresh blog is the list of the main threats to these rare freshwater fish species that were identified by IUCN... climate change is not on the list. Instead, fairly unsurprisingly, pollution, overfishing, dams, water abstraction and invasives seem to be the factors most putting these species at risk.

Some of the at-risk species include the critically endangered European eel (top); the Chornaya gudgeon (middle), found only in Ukraine; and the Jarabugo (bottom), found in Spain and Portugal. I wonder if the 'main threats' list will have changed in the future, or if perhaps these species will be long gone before climatic changes become a significant factor? Certainly climate change could indirectly already be taking effect; we know it's linked to invasive species, and I have already mentioned that dam construction projects are undertaken to safeguard water security. As this is Europe we are talking about, perhaps a more likely driver of dam building is political pressure for 'green' carbon neutral HEP energy.

Global Warming = Mass Extinction?

I've been looking at a rather sensationalist news story from the Guardian back in 2003, where the first line states that:

"Rising global temperatures over the next century could trigger a catastrophe to rival the worst mass extinction in the history of the planet"

My first reaction was skeptical, but on inspection of next few lines it seems this bold statement was actually based on some logic. Bristol based scientists had found that the Permian mass extinction 250 MYA, which saw 95% of Earth's species go extinct, was caused by only 6º C of warming. Worryingly, 6º C is the maximum warming predicted by the Intergovernmental Panel on Climate Change for a business as usual scenario... !

However, if you continue reading it turns out that the Permian extinctions were caused by massive volcanic activity, the greenhouse gas emissions of which triggered the warming. This seems rather misleading; what about the effects of huge eruptions and giant ash clouds upon dinosaur death? Don't volcanic eruptions cool the planet anyway, as the dust filled atmosphere reflects the Sun's energy back out to space? While it's arguable that reporting a "looming catastrophe" for biodiversity because of climate change will stir preventative action, I consider articles like these to simply erode public trust in climate change scientists. The article did get me thinking though - is there past evidence of climate change causing significant biodiversity loss, preferably without volcanoes muddying the waters?

Preparing European lakes and rivers for climate change

This website gives a good overview of how the current assessment systems under the Water Framework Directive are addressing the effects of climate change for aquatic environments in Europe. 

A paleoecological perspective

This post stays on the subject of global biodiversity, as I think an interesting additional perspective to the theoretical one in the last post can be found in Willis et al. (2010). This paper reviews the use of paleoecological archives to understand the rates and nature of ecological responses to climate change, partly with the aim of assessing the reliability of climate-biodiversity models with real data. Willis et al. note a huge discrepancy between a modeled and historical scenario.


Models predict that rising temperatures and CO² could transform 80% of Earth's tropical rain forest into savannah in the next 50 years; this would be a severe loss of biodiversity. However, pollen and plant macrofossils from dated tropical lake archives show that during the Eocene thermal maximum, a period with higher temperature and CO² levels than those predicted by the models for 50 years time, extremely diverse tropical rain forest extended far further over the globe than it does today. Willis et al. suggest the reason behind this is a lack of understanding of atmospheric dynamics (with regard to CO²) in the model in question. I think this real-data perspective is a hopeful one; perhaps climate change would actually increase global biodiversity if other anthropogenic threats could be 'treated'.

References:

Willis, K.J., R.M. Bailey, S.A. Bhagwat and H.J.B. Birks (2010) 'Biodiversity baselines, thresholds and resilience: testing predictions and assumptions using palaeoecological data', Trends in Ecology & Evolution, 25, 10, 583-91.

What are the prospects for global biodiversity?

I've talked about how threatened freshwater biodiversity is and what threatens it now. In this post I want to consider the outlook for global biodiversity in the future. I don't think we are yet in a state of 'biodiversity crisis' (a term frequently used on blogs and forums) as there are still hotspots of amazing diversity on the planet. Are we heading for crisis however? If so, how quickly? 

I'll look at Jenkins' (2003) paper Prospects for Biodiversity, which has been cited 103 times. This theoretical study tackles the above questions for global biodiversity by looking at what to expect by 2050. Jenkins presents an overview of other research in the area, focusing on extinction risk and population reduction in birds, terrestrial and marine mammals and freshwater fishes, habitat losses to agriculture, forest cover and wilderness. Assumptions include around 9 billion people by 2050, that IPCC predictions on climate change hold true and that humans don't behave very differently.

A key theme is huge biodiversity losses in developing countries in tropical regions as they develop. These areas - South America, sub-Saharan Africa, Indonesia and the Philippines - have suitable forested land available for conversion to agriculture, which will be needed to feed and clothe an increasing global population. Deforestation here will take a heavy toll on global biodiversity, as many of these areas are highly biodiverse with high endemism. Developed countries on the other hand, are predicted changes in distribution of species with climate change, but a fairly stable biodiversity overall. Temperature forest cover should rise and species loss in developed farmland areas slow - but these are dependent on the current green movement retaining momentum and working long term.

A recurring element is the scarcity of large animal species, in the remaining tropical forest and in the oceans, due to resource overexploitation. Freshwater biodiversity is predicted to particularly suffer. Jenkins cites WWF Living Planet Index data from 1970 - 2000 that shows freshwater biodiversity falling far faster than marine or forest, and states that human pressures on freshwater habitats will only increase. The greatest freshwater biodiversity losses will take place in urban tropical and arid areas, mainly from pollution, overfishing and water abstraction, and even in developed countries aquatic biodiversity is still predicted to worsen, this time due to invasive species.

All in all, a rather bleak picture for global biodiversity; monumental reductions in species diversity, particularly for certain types of ecosystem or taxa. Jenkins of course points out the difficulties in prediction; extinction rates are a simple concept, but deciding what they are likely to be in future is stymied by lack of knowledge. We are ignorant of the actual species diversity out there, unable to comprehensively monitor extinction in discovered species and uncertain of how many species we may save in the future.

Perhaps the most interesting point Jenkin's makes is that the predicted shift to "biotically impoverished" habitats is not expected to cause problems for humanity. This is quite contrary to much of the wider literature which cites biodiversity as hugely important for humanity as a provider of natural services (such as nutrient recycling, flood control or carbon sequestration), having important aesthetic and cultural value and as a provider of food, building and trade resources. Have a look at this and this website, which give the classic breakdown of 'why save biodiversity'.

However, "biotically impoverished" doesn't mean no biota, just a less diverse range of species. Jenkins' point does make sense; you don't really need a wide range of tree species to soak up CO², intercept rainwater or provide timber. He suggests that ecologists have yet to find compelling evidence that wild systems are better at the above mentioned functions/values than human modified ones. A person's concept of an aesthetically pleasing environment is often not a natural one - mine is the Somerset countryside, for example, a man-made landscape with far lower biodiversity than the pre-agricultral ecosystem. If conservationists fail to show that high biodiversity is highly important for human prosperity, I imagine the prospects for global biodiversity to become even more bleak.

One aspect of biodiversity Jenkins fails to mention: it's inherent value as a 'database' of genetic information and chemical products. This must be considered as having value like an insurance policy; a high biodiversity is worth maintaining just in case humans need to use it for new medicines or genetic code in the future. Finally, is this the reason we 'need' to save natural ecosystems? A key unknown in Jenkins predictions is us - he has assumed our attitude and behavior will not change "radically". Are humans prepared to make big changes to save biodiversity 'just in case' we need it later on?

References:

Jenkins, M. (2003) 'Prospects for Biodiversity', Science, 302, 1175-7.