Does “irreplaceability” tell us where to prioritise protected area management?

I was asked by The Conversation to provide some comments on an new paper published by Soizic Le Saout and colleagues this week in Science. You can read my comments and those of a number of other scientists in the article. But I thought I’d share some more thoughts on the paper here.

Update 18/11/13: Added a short paragraph about PA management effectiveness.

 The world's most irreplaceable PAs for conservation of amphibian, bird, and mammal species. (A) Global distribution. (B) Central and South America. (C) East Africa. (D) Southern and Southeast Asia. To facilitate representation, clusters of overlapping or nearby sites are presented here as a single symbol; see fig. S1 and table S2 for a full list of sites comprising 137 protected areas in 78 clusters. See SM for details. (from the Science article: https://www.sciencemag.org/content/342/6160/803/F2.expansion.html)
The world’s most irreplaceable PAs for conservation of amphibian, bird, and mammal species.
(A) Global distribution. (B) Central and South America. (C) East Africa. (D) Southern and Southeast Asia. To facilitate representation, clusters of overlapping or nearby sites are presented here as a single symbol; see fig. S1 and table S2 for a full list of sites comprising 137 protected areas in 78 clusters. See SM for details. (from the Science article: https://www.sciencemag.org/content/342/6160/803/F2.expansion.html)

“Irreplaceability” and protected area management

Essentially what this study does is to overlap maps of the current global protected area network, with the maps of distributions of major vertebrate groups: mammals, birds and amphibians.

What they do is fairly straightforward – they calculate a score which they term ‘irreplaceability’[fn1]: the weighted sum of species (i.e species richness) found in that particular protected area. The weighting is found by calculating the proportion of each species’ global range that is contained in that particular protected area.

In the paper, authors argue that their approach provides “guidance for strategically  to strengthen their collective contribution toward preventing global species extinctions.”

They identify existing protected areas across the globe which are highly ‘irreplaceable’ [fn2] (according to their measure), for which they recommend “a particularly high level of management effort and encourage global recognition as World Heritage sites”.

Does World Heritage Site status = good management?

Now, I have a couple of key issues with this argument.

First, it assumes that designating a protected area as a World Heritage Site (WHS) will ensure or increase the chance of high management effectiveness. A WHS is a source of pride and can be an iconic tourist destination – think of Australia’s Great Barrier Reef and Kakadu National Park, so it’s in a nation’s best interest to adequately protect and manage these sites.

But WHS status is no guarantee that biodiversity is free from threats in these areas – consider the current port developments proposed along the GBR coastline in Queensland, which has lead UNESCO to repeatedly warn Australian Governments of the risk that the Great Barrier Reef may be included on the List of World Heritage in Danger (there are currently 44 WHS listed as in danger).

Kakadu National Park is another of Australia’s WHS, and is highly managed – yet we are losing mammal species here at an alarming rate, through some combination of fire and feral cats in particular.

Finally, it needs to be emphasized that biodiversity ‘irreplaceability’ should not be the only criteria for identifying priority areas for management. We also need to think about:

  1. What are the key threats facing species in an area? (e.g deforestation, invasive species, fire).
  2. What are the management actions required to reduce these threats? (e.g control deforestation, control invasive species, fire management)
  3. What are the costs of these management actions?
  4. What is the benefit gained from implementing these actions?

For example, a protected area might be deemed as highly ‘irreplaceable’, but may not be under threat and so may not need greater management focus, so resources could be spent more wisely elsewhere. 

By considering the costs and benefits of management in addition to the benefit to biodiversity, we could find a very different list of priority sites compared to the sites that would be identified by considering biodiversity values (‘irreplaceability’, species richness or whatever) alone.

How can protected area management be improved?

Clearly a lack of resources is a key constraint in implementing management for conserving threatened species. But another major issue is that we often have little information available to know how effective protected area management have been in the past, so can’t be sure on what outcomes have been delivered from past management.

This lack of basic information often means that despite past and ongoing investments in conservation management, we actually don’t know what that investment has delivered for our threatened species. So an important component of improving management of protected areas would be to have greater support for and capacity to evaluate and learn from past actions.

There are a large number of approaches available to assess how effective management is in protected areas – the World Database on Protected Areas lists 40 methodologies which have been applied in over 100 countries. Systematic reviews are commonly used to assess the current evidence for the effectiveness of different conservation management actions. But a recent study by Carly Cook and others found that only 2 of 43 systematic reviews assessed were able to provide comprehensive management guidance.  So it’s important to make sure that when evaluating management effectiveness, the results are relevant to protected area managers, and also appraise the cost-effectiveness of interventions.

Drawing a long bow between high biodiversity ‘value” and priorities for management

I understand that the ‘irreplaceability’ score proposed by the authors of this study has already been supported by the IUCN and UNEP-WCMC as a “a technical basis for the selection and prioritization of areas and sites with potentially outstanding biodiversity values for World Heritage nomination” (page xi of this report).

I don’t really have an issue with the proposal to use the ‘irreplaceability’ score as one piece of information (among many others) that could help areas of “outstanding universal value” be identified as possible candidates for World Heritage nomination.  But to suggest that this information can be used to “strategically allocate management efforts among and within existing PAs” is I think going a step too far.

Footnotes

[fn 1]: It’s important to note that what Le Saout et al. call ‘irreplaceability’ is different (but related) to the most common use of the term in conservation science. In this new paper, it’s calculated as follows: imagine that a particular protected area contains two unique species: the species richness is equal to two. Species #1 has 50% of its global range in that protected area, whereas Species #2 has 100% of its global range contained in that protected area. The irreplaceability score is therefore 1*0.50 + 1*1.0 = 1.5.

The irreplaceability score of a protected area is high if it contains a large number of species with a high proportion of their global range found in that protected area, and the score is low if it contains a small number of species with a low proportion of their global range in that protected area. But  the authors alter the weighting to place a lower emphasis on cases where a small proportion of a species’ global range overlaps with a protected area – which the authors argue is more likely to be a result of a commission error than cases when a large proportion of a species’ global range overlaps with a protected area. Using the example given above, the irreplaceability score becomes 1.76.

‘Irreplaceability’ as defined by Pressey et al. (1994) and used most commonly in conservation science: a measure of the relative importance of a particular site for biodiversity conservation in terms of the potential to replace it with others in the region. Irreplaceability is a value between 0 and 1, where sites with values of 1 are essential for achieving a conservation target (e.g, if we aim to protect 30% of the range of each species) and are therefore irreplaceable.

[fn 2]: The authors identified priority protected areas as those which made top 100 in the “irreplaceability” ranking. I have my usual concerns with rankings and arbitrary cut-offs (why top 100?), but I won’t go into it here.

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