Fighting Climate Change While Maintaining Biodiversity: Can It Be Done?

Mapping co-benefits for carbon storage and biodiversity to inform conservation policy and action (2019) Soto-Navarro et al., Philosophical Transactions of the Royal Society B, https://doi.org/10.1098/rstb.2019.0128

The Crux

With the world under so many anthropogenic pressures simultaneously, trying to come up with management solutions for different issues can be a problem. Climate change and biodiversity are a great example. Storing carbon is a great way to reduce the effects of climate change, and increasing the range of forests worldwide is a great way to increase carbon storage. Yet the sort of forests that store carbon most efficiently are often poor at promoting biodiversity. They are largely made up of very similar trees, while forests that include brush, scrubs, and other layers often store less carbon, but house more biodiverse communities.

As such, finding areas that are prime specimens for a) storing carbon and b) biodiversity conservation are incredibly important, so that managers at every level (from park rangers right up to the Intergovernmental Panel on Climate Change) can know where interests overlap, and adjust plans accordingly.

What They Did

This week’s authors had some seriously ambitious goals. First on their list was to create a new map for carbon storage worldwide. This was done by calculating carbon storage per habitat type above ground, calculating below ground for these types based on IPCC guidelines, and then extrapolating these calculations to world habitat maps.

They then collated distribution maps of over 22,000 species of mammal, bird and amphibian. They then plugged these numbers in to three different biodiversity indices, which measured species richness, habitat intactness, and how threatened the habitat is. This was then used to identify habitats that were highly irreplaceable and highly threatened, and highly irreplaceable but had only a low threat level. These were intended to represent a reactive threat index (save what is threatened now) and a proactive threat index (act now before these areas are in trouble).

They then looked at the overlap between these two regions and regions of high carbon storage, looking at how well protected these areas of overlap were.

Did You Know: Biodiversity vs. Carbon Emissions

Putting together the above indices might not exactly be simple for carbon storage, but they’re much harder for biodiversity. While a carbon storage metric can be pretty simple, biodiversity is a poorly understood term. Are we talk about total species richness? Diversity in species function, phylogeny? The authors combined two metrics here, one measuring overall community richness, the other measuring community uniqueness – basically how important the area is – by looking at numbers of endemic species as well.

What They Found

There were clear contrasts between highly irreplaceable areas with high and low threat levels (pictured below). In South America for instance, much the Amazon basin was comprised of highly irreplaceable areas with a low threat level, whereas a stone’s throw away, the Northern reach of the Andes mountain was highly threatened. Madagascar and Eastern Africa were high on the reactive threat index, whereas the equatorial jungle in Africa was high on the proactive threat index.

Whilst there was high overlap between areas of high carbon storage and those high on the proactive threat index (38%), the overlap for the reactive threat index and reactive threat index was only 5%. Worryingly, very little of the regions of overlap are found in protected areas.

Screenshot from 2020-03-25 15-53-39

On the left, you can see areas which are highly irreplaceable, yet at low threat levels, in the green. On the right, dark red areas indicate regions that are highly threatened and highly irreplaceable (Image Credit: Soto-Navarro et al.)

Problems

Projects like this have ambition. However when you’re collating so many data sources, each with their own sources of error, uncertainties start to balloon. Whilst these maps provide a great guide for global policy, many smaller scale managers will have to double and triple check that the estimates of species richness and carbon storage in their area are in fact reliable. We’ll have a bit more on this uncertainty in tomorrow’s look at climate change and European forests.

So What?

I hope that reports like this make up the core of the next international report on Biodiversity and Ecosystem Services. These maps are making big assumptions, but they give a great base from which to launch more research, and more management actions.

Additionally, in ecology we (unfortunately) see a LOT of people fighting over whose cause is more important. Initiatives like this, which highlight where these two causes intersect, help create better prioritisation strategies.

Title Image Credit: Rosina Kaiser, Pixabay licence, Image Cropped

Sam Perrin is a freshwater ecologist currently completing his PhD at the Norwegian University of Science and Technology who at this point is not quite sure he was cut out for teaching seven year-olds. You can read more about his research on his Ecology for the Masses profile here, and follow him on Twitter here.

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