The better we define the richness of life on Earth, the larger the percentage we are going to lose becomes. Life won’t go extinct. The number of domains and kingdoms will very-very likely remain the same. But as we go down from phylums and orders to families and beyond the picture gets nastier with every consecutive taxonomic zoom level – ending sub subspecies.

That’s because climate change causes different forms of ecological damage, all of which in some way add up to the total biodiversity decline, a new study indicates.

From species diversity to genetic biodiversity

Scientists of the Biodiversity and Climate Research Centre (BiK-F) and other German research institutions have conducted a model study into the ecological effects of IPCC climate change scenarios.

They state predictions for biodiversity loss due to 21^st century climate change have thus far been underestimations, as these “have been predicted on the scale of taxonomically recognised morphospecies” only, so confined to the extinction risk for neatly defined species.

But, as the researchers have last weekend stated in their Nature Climate Change publication, the genetic diversity within species and subspecies also declines as they are put under strain and many local populations become extinct. This associated decline in genetic diversity also adds to sum total biodiversity loss, or intraspecific biodiversity loss.

Evolution of future species

The study looks at the example of European aquatic insects in mountainous areas. A specific species may under 2-4 degrees warming survive upstream in the Alps and parts of Scandinavia, but isolated populations in for instance the Carpathians, Pyrenees or the German Central Uplands will be lost – together with genetic diversity that was unique to such individual populations only. In the process subspecies are denied the chance of becoming independent species, as may have happened over the course of such populations’ evolutionary paths.*

[*) From another recent study we can conclude that it is practically impossible for evolution to compensate for current extinction rates. As under current extinction rates we apparently risk losing the majority of our planet’s biodiversity within a century’s time, the formation of entirely new species will take at least 10,000 times as long – and that would only be the point where system Earth would start to recover. It could take many tens or hundreds of millions of years more before the oceans could again see something equivalent to a blue whale – if ever. We should remember climate change is just one of the contributors to the biodiversity crisis.]

Climate change eats biodiversity

The reason climate change is bad for biodiversity is it creates ecological disturbances at every level, from direct heat and drought stress, to shifting of climatic zones [which forces species migrations – a process accompanied with net loss of habitat] to possible collapse of entire ecosystems, as could be the case for the Arctic – and perhaps even the Southern Ocean.

Even the fact that some species will find it much easier to adapt than others, makes further biodiversity decline likely, as this increases the risks of plagues and other food chain and ecosystem disturbances. Both for animals and for plants a domino effect has been described, where biodiversity loss acts as a positive feedback on itself.

Previous studies into the ecological effects of climate change have come up with smaller numbers for biodiversity loss, but have indeed focused on species decline only. Under IPCC scenarios an often-cited number is an expected extinction risk for around one third of large species.

According to an extinctions extrapolation in PNAS last month climate change could lead to 14 percent of all species dying out within the 21^st century.

Holocene Mass Extinction

Although history shows large (and geologically ‘sudden’) climatic changes can be very potent at creating extinction events, currently climate change is just one of several main contributors to the biodiversity crisis.

In order to prevent rapid extinctions on land much also depends on establishing, connecting and preserving nature reserves and other conservation efforts – halting tropical deforestation in particular, because the rainforests are a crucial refuge for both fauna and flora. They may not receive as much attention as an endangered forest primate, but many plant species also risk extinction, and their current threat seems of similar proportions.

For the oceans the anthropogenic environmental stressors of the 21^st century are equally diverse. Ocean warming [and possible associated changes to the thermohaline circulation] is again just one factor, next to overfishing, pollution & anoxia, and ocean acidification. Altogether, the blue planet could be at the brink of the same extinction event that is also approaching the green planet, terrestrial Earth.

The Holocene Anthropocene boundary

A Nature study earlier this year has looked at marine and terrestrial biodiversity threats combined – and found for instance 75 percent of all mammal species to be at risk of extinction within 300 years, and defined such a massive loss of biodiversity as establishing the Earth’s sixth mass extinction event.

That would mean the combined effort of a couple of billion human beings, relentlessly producing and consuming over a couple of centuries time, would somehow have very creatively managed to outweigh the impact of the PETM methane clathrate bomb.

Because the Paleocene-Eocene may be visible as a large extinction event in Earth’s fossil record, too many species survived to make it officially classify as being one of the [thus far 5] true mass extinctions. The Holocene-Anthropocene Responsibility Minimum may be bigger news – should there be geography classes, epochs from now.

From theory to the actual atmosphere

Oh yeah, one final note: the new study’s model outcome range depends on IPCC SRES scenarios. Just like we saw yesterday bad things [the upper range: 84% biodiversity loss] happen under the business as usual A2 scenario [ecologically ‘friendly’ B2 gives us 67% damage]. Worse things happen in reality though. We somehow managed to surpass the A2 emissions – burning yet more coal and emitting all that carbon into the actual atmosphere, instead of some computer model. And the failure of Copenhagen means we chose not to get back on track.

So sorry. We will really try our bests to find some good news after this, to cheer you up again. It’s promised. But I’ll first need a couple of days off…

© Rolf Schuttenhelm | www.bitsofscience.org