Bendix, J; Behling, H; Peters, T; Richter, M; Beck, E: Functional biodiversity and climate change along an altitudinal gradient in a tropical mountain rainforest., , In: Tscharnke, T. et al. (Eds.): Tropical rainforests and agroforests under global change. Springer Berlin-Heidelberg, 3-33 (2009), doi:10.1007/978-3-642-00493-3_11 | |
Abstract: This article investigates possible consequences of climate change for a hotspot of tropical biodiversity, exemplified by a comparatively small area of a neotropical mountain rain forest in the eastern range of the South Ecuadorian Andes. In the introduction, several approaches for such predictions are evaluated with respect to their applicability to the eco-region. After a short presentation of the research area and its biodiversity, climate and vegetation development during the Holocene is described showing the range of possible fluctuations between Puna-like grassland and tropical mountain forest. Data of climate dynamics during the past 50 – 60 years, covering several ENSO (El Niño Southern Oscillation) events, suggest a significant increase in temperature but no dramatic changes in the precipitation regimes of the region. Due to the altitudinal span of the area, the rise in temperature will shift the ecothermic belts by several hundred meters uphill and thus increase the distribution ranges of ectothermic organisms. To assess the consequences of this shift on biodiversity two model approaches were applied, namely the species-area-approach and the energetic-equivalence rule, using the extremely diverse insect group of moths. Combining both approaches the consequences of a climate change Teja Tscharntke, Christoph Leuschner, Edzo Veldkamp, Heiko Faust, Edi Guhardja, Arifuddin Bidin (editors): Tropical rainforests and agroforests under global change: Ecological and socio-economic valuations. Springer Berlin 2010, pp 239–268 240 J. Bendix et al. can be estimated for the various scenarios of greenhouse gas emissions published by the International Panel on Climate Change (IPCC 2007). Applying the most realistic scenario A1B a reduction of moth species by 31% until the year 2100 can be predicted for the RBSF area. Due to their greater life-span, woody plants are much more resilient to climate change, especially so in a megadiverse forest with usually small population sizes. Therefore impacts of global warming on the local vegetation can only be assessed on the basis of qualitative data of the forest structure rather than of the floristic composition. The most conspicuous trait of the tropical mountain rain forest in the region is the low elevation of the upper tree-line which on average is by 1000 to 1500 m lower than in the other parts of the tropical Andes. Due to the particular orographic situation, the extreme environmental conditions (quasipermanent easterly storms carrying a tremendous load of precipitation) do not allow growth of trees in the peak regions of the mountains. Only if the prevailing trade-wind system dampened and the mountain range received less precipitation, a change of the environmental conditions could be expected resulting in a situation like in the early and mid Holocene, when a forest covered the entire mountain range. However, up to present, symptoms for such a change are lacking. A final outlook comments on the priority ranking of climate change vs. direct anthropogenic impacts with respect to conservation measures. For the investigated tropical forest ecosystem a reduction of human impact is more urgent than ever. |