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Monday, 3 September 2012

How to plan conservation area in a highly fragmented landscape? - Ilkka Hanski's plenary on ECCB2012

In a landscape like Europe, conservation area planning almost inevitably faces the challenge of high degree of fragmentation. How to counter the effects of fragmentation? Last day plenary in ECCB2012 given by Prof Ilkka Hanski addressed this issue providing insight to the revised species-area relationship model and a suggestion for conservation planning practice.

I. Hanski is waiting for questions at ECCB2012
(chair: Gábor Lövei)
Starting with the case study of Glanville Fritillary, a butterfly, Hanski showed the non-linear relationship of habitat loss and species abundance. What does it mean in practice? There is a point in habitat loss when the species, which showed a steady decrease in abundance, suddenly disappears. This is called the extinction threshold - the point when habitat loss reaches a point (i.e 10-15% of the habitat is left), from where there is no return for a species. Therefore, a new model of species- area relationship, including the effects of fragmentation are to be used for situations when less than 15% of the habitat is left.

It is also important to realize that sometimes detected presence of a species does not reveal the actual threat imposed on the species survival. This is called the extinction debt concept: as Hanski showed, deforestation that happened a century ago resulting a highly fragmented forested landscape leads to the ultimate loss of forest-related species now. These species are the "living dead" - species being detected in the area, however, in their way to extinction.

How can we plan effective conservation in highly fragmented areas? Hanski's results show that it is better to conserve areas of clustered habitat patches than conserve habitat patches which are randomly distributed.  In his paper published in AMBIO, 2011, he suggests a framework of large-scale habitat conservation: the "third-of-third approach: a third of the land area is managed as multi-use conservation landscapes (CL), within which a third of the area is protected. This means that a third of the third, about 10% of the total area, is protected" (Hanski, 2011). This might be smaller than the Nagoya target of 17 %, but it is added to the exisitng network of protected areas.

This concept raises many questions: how these protected areas within the CL-s could be really protected effectively in a matrix of land-use? What does (should) exactly "multi-use" mean? How can the non-protected area of the CL-s ensure large-scale connectivity between the protected patches? There surely are many more points to raise, however,  this concept is  relevant to be considered in the land sparing - land sharing debate, and it addresses the challenges of conservation in a human-dominated landscape.

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