Global Warming May Cause Higher Loss of Biodiversity Than Previously Thought

White branches show lost genetic lineages (no climatically suitable areas projected) in 2080 if global temperature increases by four degrees. (Credit: Copyright Miklos Bálint et al)

Science Daily  — If global warming continues as expected, it is estimated that almost a third of all flora and fauna species worldwide could become extinct. Scientists from the Biodiversity and Climate Research Centre (Biodiversität und Klima Forschungszentrum, BiK-F) and the SENCKENBERG Gesellschaft für Naturkunde discovered that the proportion of actual biodiversity loss should quite clearly be revised upwards: by 2080, more than 80 % of genetic diversity within species may disappear in certain groups of organisms, according to researchers in the title story of the journal Nature Climate Change. The study is the first world-wide to quantify the loss of biological diversity on the basis of genetic diversity.

In a pioneering study, scientists from the Biodiversity and Climate Research Centre (BiK-F) and the Senckenberg Gesellschaft für Naturkunde have now examined the influence of global warming on genetic diversity within species.Most common models on the effects of climate change on flora and fauna concentrate on "classically" described species, in other words groups of organisms that are clearly separate from each other morphologically. Until now, however, so-called cryptic diversity has not been taken into account. It encompasses the diversity of genetic variations and deviations within described species, and can only be researched fully since the development of molecular-genetic methods. As well as the diversity of ecosystems and species, these genetic variations are a central part of global biodiversity.Over 80 percent of genetic variations may become extinct

The distribution of nine European aquatic insect species, which still exist in the headwaters of streams in many high mountain areas in Central and Northern Europe, was modelled. They have already been widely researched, which means that the regional distribution of the inner-species diversity and the existence of morphologically cryptic, evolutionary lines are already known.

If global warming does take place in the range that is predicted by the Intergovernmental Panel on Climate Change (IPCC), these creatures will be pushed back to only a few small refugia, e.g. in Scandinavia and the Alps, by 2080, according to model calculations. If Europe's climate warms up by up to two degrees only, eight of the species examined will survive, at least in some areas; with an increase in temperature of 4 degrees, six species will probably survive in some areas by 2080. However, due to the extinction of local populations, genetic diversity will decline to a much more dramatic extent.

According to the most pessimistic projections, 84 percent of all genetic variations would die out by 2080; in the "best case," two-thirds of all genetic variations would disappear. The aquatic insects that were examined are representative for many species of mountainous regions of Central Europe.

Slim chances in the long term for the emergence of new species and species survival

Carsten Nowak of the Biodiversity and Climate Research Centre (BiK-F) and the Senckenberg Gesellschaft für Naturkunde, explains: "Our models of future distribution show that the "species" as such will usually survive. However, the majority of the genetic variations, which in each case exist only in certain places, will not survive. This means that self-contained evolutionary lineages in other regions such as the Carpathians, Pyrenees or the German Central Uplands will be lost. Many of these lines are currently in the process of developing into separate species, but will become extinct before this is achieved, if our model calculations are accurate."

Genetic variation within a species is also important for adaptability to changing habitats and climatic conditions. Their loss therefore also reduces the chances for species survival in the long term.

New approach for conservation

So the extinction of species hides an ever greater loss, in the form of the massive disappearance of genetic diversity. "The loss of biodiversity that can be expected in the course of global warming has probably been greatly underestimated in previous studies, which have only referred to species numbers," says Steffen Pauls, Biodiversity and Climate Research Centre (BiK-F), of the findings. However, there is also an opportunity to use genetic diversity in order to make conservation and environmental protection more efficient.

A topic that is subject to much discussion at present is how to deal with conservation areas under the conditions of climate change. The authors of the study urge that conservation areas should also be oriented to places where both a suitable habitat for the species and a high degree of inner-species genetic diversity can be preserved in the future. "It is high time," says Nowak, "that we see biodiversity not only as a static accumulation of species, but rather as a variety of evolutionary lines that are in a constant state of change. The loss of one such line, irrespective of whether it is defined today as a "species" in itself, could potentially mean a massive loss in biodiversity in the future."