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A considerably extended two-dimensional version of the famous Lovelock-Watson model for geosphere-biosphere interactions ("Daisyworld") is employed to investigate the impact of habitat fragmentation. The latter is dynamically modelled through the standard percolation process first introduced by solid state theory. It is found that the connectivity of the space accessible for life is crucial for ecological performance. In particular, the self-stabilizing capacity of the biosphere strongly depends on the fragmentation topology. An extremely rich and partially counter-intuitive eco-dynamics is observed when a simple community structure, consisting of plants and herbivores, is introduced. Quite remarkably, high herbivore vitality destroys the stability of the entire biosphere in a way reminiscent of "desertification". (C) 1999 Elsevier Science B.V. All rights reserved.