Biodiversity Hotspots have nearly burnt out

10 07 2014

dying embersI recently came across a really important paper that might have flown under the radar for many people. For this reason, I’m highlighting it here and will soon write up a F1000 Recommendation. This is news that needs to be heard, understood and appreciated by conservation scientists and environmental policy makers everywhere.

Sean Sloan and colleagues (including conservation guru, Bill Laurance) have just published a paper entitled Remaining natural vegetation in the global biodiversity hotspots in Biological Conservation, and it we are presented with some rather depressing and utterly sobering data.

Unless you’ve been living under a rock for the past 20 years, you’ll have at least heard of the global Biodiversity Hotspots (you can even download GIS layers for them here). From an initial 10, to 25, they increased penultimately to 34; most recently with the addition of the Forests of East Australia, we now have 35 Biodiversity Hotspots across the globe. The idea behind these is to focus conservation attention, investment and intervention in the areas with the most unique species assemblages that are simultaneously experiencing the most human-caused disturbances.

Indeed, today’s 35 Biodiversity Hotspots include 77 % of all mammal, bird, reptile and amphibian species (holy shit!). They also harbour about half of all plant species, and 42 % of endemic (not found anywhere else) terrestrial vertebrates. They also have the dubious honour of hosting 75 % of all endangered terrestrial vertebrates (holy, holy shit!). Interestingly, it’s not just amazing biological diversity that typifies the Hotspots – human cultural diversity is also high within them, with about half of the world’s indigenous languages found therein.

Of course, to qualify as a Biodiversity Hotspot, an area needs to be under threat – and under threat they area. There are now over 2 billion people living within Biodiversity Hotspots, so it comes as no surprise that about 85 % of their area is modified by humans in some way.

A key component of the original delimitation of the Hotspots was the amount of ‘natural intact vegetation’ (mainly undisturbed by humans) within an area. While revolutionary 30 years ago, these estimates were based to a large extent on expert opinions, undocumented assessments and poor satellite data. Other independent estimates have been applied to the Hotspots to estimate their natural intact vegetation, but these have rarely been made specifically for Hotspots, and they have tended to discount non-forest or open-forest vegetation formations (e.g., savannas & shrublands).

So with horribly out-of-date vegetation assessments fraught with error and uncertainty, Sloan and colleagues set out to estimate what’s really going on vegetation-wise in the world’s 35 Biodiversity Hotspots. What they found is frightening, to say the least.

Their very detailed approach can be summarised in two phases. First, they assessed the vegetation condition, spatial pattern, and local ecological appropriateness of each land-cover class of the global GlobCover 2009 satellite-image classification for each ecoregion using moderate- and high-resolution satellite imagery. Herein, they defined the ‘naturally occurring’ areas to which they applied their second method to fine-tune the estimates. There, they clipped the disturbed areas using various disturbance maps. The final result was an estimate of ‘natural intact vegetation’ which they defined as “mature vegetation in its natural state having minimal signs of human perturbation”.

According to their methods, Hotspots retain 3,545,975 km2 of natural intact vegetation, or just 14.9% of their original extent. As such, they conclude that they are generally much more perturbed than previously thought. Of the 20 Hotspots with ≥ 20 % of such vegetation as assessed by Mittermeier and colleagues in 2004, now only 7 of them have this much.

They also found that the worst cases are now even worse; there are now 17 Hotspots with ≤ 10% natural intact vegetation, compared to 10 estimated by Mittermeier et al. (2004).

There is a glimmer of positive news though for some Hotspots: 10–12 of them have an area of natural intact vegetation greater than previously estimated. These tend to be mountainous, Mediterranean-type or non-tropical Hotspots.

The take-home message overall is, however, very depressing, with the general state of the global Biodiversity Hotspots more critical than ever previously appreciated, particularly for those originally thought to be  relatively intact.

I’m looking forward to catching up with Sean and others in Cairns at the Association for Tropical Biology and Conservation Annual Conference in a little over a week to discuss this paper in more detail. In response to the sobering news, I might have to get drunk with them.

CJA Bradshaw



3 responses

16 08 2014

Reblogged this on for Biodiversity's sake!.

22 07 2014

Not wanting to encourage a two day binge, I have to point out the NIV estimates are almost certainly too high. Satellite images do not show understory plants and soil-surface microorganisms. In forests, these are the principal determinants of botanical diversity, and they are the first to go as grazing and gathering occur.

10 07 2014

Sean has just confirmed that inebriation is indeed required and will ensue. I shall report the aftermath (or maybe not).

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