Wednesday, 20 August 2003

Biodiversity and the Jenga Principle

and other musings by John Burton

Biodiversity is a term first used in 1985 and Sir Martin Holdgate the former Director of IUCN regarded it as the 'Total sum of life's variety on Earth, expressed at the genetic, species and ecosystem level' . In fact the term has entered into common parlance as a synonym for species diversity, and is in consequence, often misleading. Areas that are important for biodiversity are indeed often species rich, but an over-emphasis on species-rich, so-called ‘biodiversity hotspots’ can not only be misleading, but detrimental to conservation.

One of the objects of ‘hotspots’ was to prioritise conservation action, but such prioritisation is a gross simplication, and fraught with problems. First and foremost there is the issue of the reliability of the data it is based on. It is not uncommon for birds to be used as indicator’ species. This is because it is claimed that birds are among the best-studied taxa, with relatively few new taxa to be described. This claim is not entirely justified, since recent years have actually seen an upsurge in new taxa being recognised. There is also the question as to whether or not one group of taxa can be used to reflect species richness in others. BirdLife published such comparisons but the results were very disappointing, and showed very little convergence between the distribution of mammalian, reptilian and amphibian narrow endemics with birds or with each other.

A glance at any of the maps of the so-called biodiversity hotspots shows that there is a huge concentration in the tropical regions, but hardly any of these regions have been studied anything like as well as Europe or North America, where new species continue to be described every year. Other concentrations occur where there is large altitudinal variation in a relative small area, such as the Eastern Mediterranean. Areas such as Patagonia, the Putsa, Gobi Desert are ignored despite having many interesting and unique species, including endemics.

And this is where Jenga comes in. Most readers will know that Jenga is a simple game of manual dexterity. A tower of wood blocks is created, and then the contestants take it in turns to remove blocks without causing the tower to collapse, but leaving the top layer intact. If a large tower is created, clearly under normal circumstances, more pieces can be removed before it collapses, than from a small tower. If the blocks are used to represent species within an ecosystem, the analogy works pretty well. A simple ecosystem, (pampas) is formed from large blocks (species) but relatively few of them, to create the entire tower (biomass). As a tower it is relatively stable, but as soon as one or two blocks are removed near the base, the slightest jolt will lead it to collapse (other species become extinct). A complex ecosystem (rainforest) is not even a single tower, but a complex series of towers, more like a pyramid, comprising hundreds of blocks. Lots of blocks can be removed before serious damage occurs to the structure, even from near the base.

These are the extremes, and I am sure the analogy can be developed further -- it would also make an interesting and marketable game. But it is in the less clearly defined habitats – those of the temperate regions, the concept is most likely to be useful.

What we should be looking at are habitats that are likely to cease to operate as ecosystems (Jenga towers) and concentrate on conserving those. Using this approach, I believe it is possible to prioritise conservation action. Madagascar, which is clearly comprised of a tower of unique blocks, has already lost most of its base layers, and so compared with the Amazon or Congo, is much nearer to collapse.

And applying the concept to Europe it is apparent that the whole region is in serious danger. In the past 50 years so much of what was at least partially able to support an ecosystem (farmland) has undergone ‘desertification’, that it is unlikely that the rest of the ecosystems can survive. The disappearance of birds such as the house sparrow, may even be a symptom of this collapse.

Previous experience has led me to always question the basis of setting priorities. In 1988 I was involved with the creation of the Programme for Belize, a conservation initiative to acquire land in Central America. Several international conservation bodies were approached for support, but the World Wildlife Fund in the UK declined to put its name to the project at the time, because it was not a ‘priority’ area. 15 years on, with the benefit of hindsight, we can now state that that area is part of the largest remaining continuous tract of forest in the whole of northern Central America. It is one of the few forests capable of sustaining viable populations of species such as Jaguar and Puma, as well as providing habitat for a wide range of other species. The problem with most of the prioritisation systems that have been used recently, is that they have usually been developed by biologists and scientists, and priorities do not only involve science -- even though scientists might argue they take other factors into account. Counting numbers of species, and degrees of rarity is only part of the equation, and in some cases a relatively unimportant part. Other factors that need to be taken into account include the following:
  • Economic considerations: What is the cost of buying or protecting the land? Can it generate income? Can it be self sustaining? What subsidies are needed?
  • Political considerations: Is there a local will to conserve it? What happens if outsiders become involved?. NIMBYism and the reverse. And there are many, many other considerations that need to be taken into account.
  • Spatial considerations: How big is the area? Can it be protected? How near is it to other protected areas? How does it relate to the economic geography of the surrounding country?

The conclusion many conservationists would reach after considering all the above, as well as the huge range of factors normally considered when evaluating endangered species, is that each case needs to be treated on its own merits, and that the world is in such a state of crisis that ALL remaining natural habitats are under threat of some sort and need protection and conservation.My personal conclusion is that the only way of implementing a realistic prioritisation is opportunistically. Too many of the world’s conservation bodies are sitting on piles of cash and/or carrying out yet more research. Truly a case of fiddling when Rome is nearly burned to the ground. It would be interesting to have some PhD students carry out research into the economics of conservation research, to look at what has been spent on endangered species research over the past 40 years, and compare that with other uses of the money, such as land acquisition. How many millions of dollars have been spent on researching elephants, rhinos tigers and gorillas? How many reserves could have been bought and protected with that money?

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