Losing streak

15 July 2016

Published in Science: International research including from the CSIRO has provided the most comprehensive quantification of global biodiversity change to date. It shows that global biodiversity has fallen to 84%, and across 58% of the Earth's surface species diversity has dropped to an extend that may critically impact on crucial services biodiversity provides.

Using a database of more than 2.3 million records of more than 39,100 species across 18,600 sites, the researchers established a map that provides key insights into the current extent of biodiversity losses.

For example, it reveals that global biodiversity has fallen to 84.6% of its original value (and to 88% taking into account the emergence of new species).

This is below a 'safe' limit set at 90%. It is a precautionary value based on the hypotheses that a drop of species in a given habitat below 90% of their original abundance may critically threaten a wide range of important services - such as crop pollination, waste decomposition, and regulation of the global carbon cycle.

The scope of the study encompasses 14 different biomes, which describes areas of similar climate and environment. Not all type of biomes were found to be affected in the same way by the impact of land-use pressures. Thus, the impact on biodiversity was more pronounced in grasslands, and less in tundra and boreal forests.

Overall, though, the study suggests nine of the 14 terrestrial biomes have surpassed the suggested threshold for biodiversity.

However, the researchers acknowledge that this needs to be interpreted with care. For example, when they included the emergence of new species, only seven of the 14 biomes were under the 'safe limit'.

The authors also note that there is a need to understand the effects of emerging new species in a given region on ecosystem function.

This is also discussed in an Perspective article by Tom H. Oliver accompanying the research paper, which highlights that the high levels of uncertainty around biodiversity change appear to hamper commitment to action.

In an expert reaction to the research, Professor Bill Sherwin, UNSW, noted that the researchers considered not just species richness, but also abundance and function.

"Far too many conservation studies consider only richness (the number of different species), which can be quite unrealistic."

However, he also remarked on the limitations of the study, for example that it did not consider invasive species and their potential negative impacts. He also pointed at the potential effects of climate change. In the case of Australia, for example, "soon many areas of Australia will have a combination of physical conditions that is unlike anything that currently exists anywhere in Australia".