Migration of species

As stated above, an important issue related to climate change is migration of species. The expected migration caused by changes in temperature is a poleward migration and hence (sub-)tropical biomes will migrate from the equator to the direction of the poles. The migration is a direct result of the law of maximum and minimum that determines the reach of a biome. If the rate of the migration of biotopes is too high, the species which normally live in this biotope can not keep pace. It is possible these species will become extinct, but these impacts seem to be small (Morgan et al., 2001). An analysis for species of birds, butterflies and herbs resulted in a mean shift of the range boundaries of 6.4 km per decade poleward, or 6.4 m per decade upward (Parmesan and Yohe, 2003). Another outcome of this study was the mean shift to an earlier spring of 2.3 days per decade. In some regions the growth rate of trees is decreasing (Barber et al., 2000) and in other regions the changed circumstances have led to the replacement of one tree species by another (Allen and Breshears, 1998). In history, similar shifts and changes in vegetation have occurred during the alternation between glacial periods and deglaciation periods.

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