Cost, not biodiversity, dictates decision to conserve

26 08 2008

One for the Potential list:

originalEuroGreen_LogoI’ve just read a great new paper by Bode et al. (2008) entitled Cost-effective global conservation spending is robust to taxonomic group.

After the hugely influential biodiversity ‘hotspot concept hit the global stage, there was a series of subsequent research papers examining just how we should measure the ‘biodiversity’ component of areas needing to be conserved (and invested in). The problem was that depending on which taxa you looked at, and what measure of ‘biodiversity’ you used (e.g., species richness, endemism, latent threat, evolutionary potential, functional redundancy), the priority list of where, how much and when to invest in conservation differed quite a lot. In other words, the congruency among listed areas was rather low (summarised nicely in Thomas Brooks‘ paper in Science Global biodiversity conservation priorities and examined also by Orme et al. 2005). This causes all sorts of problems for conservation investment planners – what to invest in and where?

Bode and colleagues’ newest paper demonstrates at least for endemism, the taxon on which you base your assessment is much less important for maximising species conservation than factors such as land cost and the degree of threat (e.g., as measured by the IUCN Red List).

Of course, their findings could be considered too simplistic because they don’t (couldn’t) evaluate other potentially more important components of ‘biodiversity’ such as genetic history (evolutionary potential) or ecological functional redundancy (the idea that a species becomes more important to conserve if no other species provide the same ecosystem functions); however, I think this paper is something of a landmark in that it shows that ‘socio-economic’ uncertainty generally outweighs uncertainty due to biodiversity measures. The long and short of this is that planners should start investing if there is evidence of heightened threat and land is cheap.

A few other missing bits means that the paper is more heuristic than prescriptive (something the authors state right up front). There is no attempt to take biodiversity, threat or land cost changes arising from climate change into account (see relevant post here), so some of the priorities are questionable. Related to this is the idea of latent risk (see relevant paper by Cardillo et al. 2006) – what’s not necessarily threatened now but likely will be in the very near future. Also, only a small percentage of species are listed in the IUCN Red List (see relevant post here), so perhaps we’re missing some important trends. Finally, I had to note that almost all the priority areas outlined in the paper happened to be in the tropics, which stands to reason given the current and ongoing extinction crisis occurring in this realm. See a more detailed post on ‘tropical turmoil‘.

Despite the caveats, I think this could provide a way forward to the conservation planning stalemate.

CJA Bradshaw

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Classics: Biodiversity Hotspots

25 08 2008

‘Classics’ is a category of posts highlighting research that has made a real difference to biodiversity conservation. All posts in this category will be permanently displayed on the Classics page of ConservationBytes.com

info-chap7-slide-pic03Myers, N., Mittermeier, R.A., Mittermeier, C.G., da Fonseca, G.A.B. & Kent, J. (2000). Biodiversity hotspots for conservation priorities. Nature, 403, 853-858

According to Google Scholar, this paper has over 2500 citations. Even though it was published less than a decade ago, already Myers and colleagues’ ‘hotspots’ concept has become the classic lexicon for, as they defined it, areas with high species endemism and degradation by humans. In other words, these are places on the planet (originally only terrestrial, but the concept has been extended to the marine realm) where at the current rates of habitat loss, exploitation, etc., we stand to lose far more irreplaceable species. The concept has been criticised for various incapacities to account for all types of threats – indeed, many other prioritisation criteria have been proposed (assessed nicely by Brooks et al. 2006 and Orme et al. 2005), but it’s the general idea proposed by Myers and colleagues that has set the conservation policy stage for most countries. One little gripe here – although the concept ostensibly means areas of high endemic species richness AND associated threat, people often take the term ‘hotspot’ to mean just a place with lots of species. Not so. Ah, the intangible concept of biodiversity!

CJA Bradshaw

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The extinction vortex

25 08 2008

One for the Potential list:

vortexFirst coined by Gilpin & Soulé in 1986, the extinction vortex is the term used to describe the process that declining populations undergo when”a mutual reinforcement occurs among biotic and abiotic processes that drives population size downward to extinction” (Brook, Sodhi & Bradshaw 2008).

Although several types of ‘vortices’ were labelled by Gilpin & Soulé, the concept was subsequently simplified by Caughley (1994) in his famous paper on the declining and small population paradigms, but only truly quantified for the first time by Fagan & Holmes (2006) in their Ecology Letters paper entitled Quantifying the extinction vortex.

Fagan and Holmes compiled a small time-series database of ten vertebrate species (two mammals, five birds, two reptiles and a fish) whose final extinction was witnessed via monitoring. They confirmed that the time to extinction scales to the logarithm of population size. In other words, as populations decline, the time elapsing before extinction occurs becomes rapidly (exponentially) smaller and smaller. They also found greater rates of population decline nearer to the time of extinction than earlier in the population’s history, confirming the expectation that genetic deterioration contributes to a general corrosion of individual performance (fitness). Finally, they found that the variability in abundance was also highest as populations approached extinction, irrespective of population size, thus demonstrating indirectly that random environmental fluctuations take over to cause the final extinction regardless of what caused the population to decline in the first place.

What does this mean for conservation efforts? It was fundamentally the first empirical demonstration that the theory of accelerating extinction proneness occurs as populations decline, meaning that all attempts must be made to ensure large population sizes if there is any chance of maintaining long-term persistence. This relates to the minimum viable population size concept that should underscore each and every recovery and target set or desired for any population in trouble or under conservation scrutiny.

CJA Bradshaw

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Investor creates first tropical biodiversity credits

23 08 2008

Post reproduced from TakeCover08:

An Australian investment company has launched what it describes as the first tropical biodiversity credit scheme, Mongabay.com reports (more detail here).

New Forests, a Sydney-based firm, has established the Malua Wildlife Habitat Conservation Bank in Malaysia as an attempt to raise funds for rainforest conservation.

The “Malua BioBank” will use an investment from a private equity fund to restore and protect 34,000 hectares of formerly logged forest.

The area will serve as a buffer between biological-rich forest reserve and oil palm plantations.

The credit scheme will generate “Biodiversity Conservation Certificates”, which will be sold to bankroll a perpetual conservation trust and produce a return on investment for the Sabah Government and the private equity fund.

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Classics: Declining and small population paradigms

23 08 2008

‘Classics’ is a category of posts highlighting research that has made a real difference to biodiversity conservation. All posts in this category will be permanently displayed on the Classics page of ConservationBytes.com

image0032Caughley, G. (1994). Directions in conservation biology. Journal of Animal Ecology, 63, 215-244.

Cited around 800 times according to Google Scholar, this classic paper demonstrated the essential difference between the two major paradigms dominating the discipline of conservation biology: (1) the ‘declining’ population paradigm, and the (2) ‘small’ population paradigm. The declining population paradigm is the identification and management of the processes that depress the demographic rate of a species and cause its populations to decline deterministically, whereas the small population paradigm is the study of the dynamics of small populations that have declined owing to some (deterministic) perturbation and which are more susceptible to extinction via chance (stochastic) events. Put simply, the forces that drive populations into decline aren’t necessarily those that drive the final nail into a species’ coffin – we must manage for both types of processes  simultaneously , and the synergies between them, if we want to reduce the likelihood of species going extinct.

CJA Bradshaw

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Classics: Red List of Threatened Species

22 08 2008

‘Classics’ is a category of posts highlighting research that has made a real difference to biodiversity conservation. All posts in this category will be permanently displayed on the Classics page of ConservationBytes.com

3_en_redlist_rgb_sitoMace, G.M. & Lande, R. (1991). Assessing extinction threats: toward a re-evaluation of IUCN threatened species categories. Conservation Biology, 51, 148-157.

I was recently fortunate enough to have the chance to speak with Georgina Mace, current president of the Society for Conservation Biology, to ask her which was the defining paper behind the hugely influential IUCN Red List of Threatened Species. There is little doubt that the Red List has been one of the most influential conservation policy tools constructed. Used as the global standard for the assessment of threat (i.e., extinction risk) for now > 40000 species, the Red List is the main tool by which most people judge the status, extinction risk, and recovery potential of threatened species worldwide. Far from complete (e.g., it covers about 2 % of described species), the Red List is an evolving and improving assessment by the world’s best experts. It has become very much more than just a ‘list’.

Indeed, it is used often in the conservation ecology literature as a proxy for extinction risk (although see post on Minimum Viable Population size for some counter-arguments to that idea). We’ve used it that way ourselves in several recent papers (see below), and there are plenty of other examples. From extinction theory to policy implementation, Mace & Lande’s contribution to biodiversity conservation via the Red List was a major step forward.

See also:

CJA Bradshaw

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