Kakadu National Park, Australia’s premier National Park, is being transformed by global climate change. Using advanced statistical analyses of historical sequences of aerial photography, Professor David Bowman, from the University of Tasmania, and his research team were able to show that woody plants have proliferated in the last 50 years within Kakadu’s savanna landscape and have transformed sections of treeless floodplains into tracts of scrub.
Such marked increase in woody cover is surprising given concerns about the impact of hostile fire regimes on the Park and the legacy-effects of an irruption of feral water buffalo that was finally brought under control by a sustained control programme in the 1980s. However, the analysis is consistent with a number of previous related studies undertaken by Bowman’s team. The cause of the expansion is related to a trend of increased rainfall in northern Australia and possibly the ‘fertilizer effect’ of increased atmospheric carbon dioxide, which favours growth of woody plants over that of tropical grasses.
The increase in woody vegetation has accelerated over the last 50 years because woody patch growth increases in a compound fashion. Such a non-linear pattern of woody increase has contributed to the erroneous belief that buffalo were the cause of the woody growth on the previously treeless floodplains – in fact the analysis showed that the buffalo control programme merely coincided with the dramatic expansion of woody plants.
The study is important as it shows the pervasive effects of global change on regional ecosystems. The expansion of woody plants is degrading wildlife habitat quality of Kakadu National Park’s iconic wetlands, particularly for water-birds that need treeless conditions. The upside, however, is that the park is capturing carbon in the woody growth. However, these effects may be transitory, as the IPCC’s recent climate change assessment has identified the Kakadu freshwater floodplains as being at risk of destruction due to sea level rise during this century.
Source paper: Bowman, D. M. J. S., Riley, J. E., Boggs, G. S. , Lehmann, C. E. R. & Prior, L. D. (2008) Do feral buffalo (Bubalus bubalis) explain the increase of woody cover in savannas of Kakadu National Park, Australia? Journal of Biogeography, doi: 10.1111/j.1365-2699.2008.01934.x.
Source of article: Journal of Biogeography highlighted papers