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The Monsoon Rainforests of Northern Australia
Volume 9, Number 49: 6 December 2006

Banfai and Bowman (2006) report that "a number of processes are thought to be threatening the ecological integrity of monsoon rainforests in Northern Australia," including "the combined effects of an increase in late dry season fires, feral animal damage and weed invasion." In addition, climate alarmists everywhere contend that rainforests the world over are in danger of succumbing to the supposedly deleterious effects of the continuation of what they call the unprecedented global warming of the late 20th century, which they claim was driven by concomitant unprecedented increases in the air's CO2 content, which together comprise the "twin evils" of what we call the radical environmentalist movement.

Against this backdrop of despair, the two Australian researchers from Charles Darwin University's School for Environmental Research decided to test this retracting rainforest claim with a comprehensive repeat aerial photography study of the Northern Territory's Kakadu National Park, where monsoon rainforest exists as an archipelago of hundreds of small patches scattered within a larger eucalypt savanna matrix. In this undertaking, in the words of the two scientists, "changes to the boundaries of 50 monsoon rainforest patches were assessed using temporal sequences of digitized aerial photography [taken in 1964, 1984, 1991 and 2004], with a view to understanding the relative importance of the drivers of change."

So what did they find?

Banfai and Bowman report that "rainforest patches increased in size between 1964 and 2004 by an average of 28.8%," and after lengthy analyses of several phenomena that might possibly have been responsible for the range increases, they concluded that "the expansion is likely to have been primarily driven by increases in variables such as rainfall and atmospheric CO2." In this regard, for example, they note that "the average [area] change for dry rainforests from 1964 to 2004 was an increase of 42.1%, whereas for wet rainforests [the increase] was one-third of this at 13.1%." In addition, in the case of dry rainforests, they report there was "an almost linear increase in rainforest area over the study period," in harmony with the concomitant upward trends of both atmospheric CO2 and rainfall.

In further support of the validity of their findings, and "contrary to the view that monsoon rainforests are contracting," which is one of the chief pessimistic mantras of the world's climate alarmists, the two researchers inform us that other repeat aerial photography studies conducted in Northern Australia have also revealed rainforest "expansion at the expense of more open vegetation." These studies include those of monsoon rainforests in Litchfield National Park near Darwin (Bowman et al., 2001) - where forest patches nearly doubled in size between 1941 and 1994 - and in the Gulf of Carpentaria (Bowman et al., in press). In addition, they write that "these changes parallel the observed expansion of tropical rainforest on the east coast of Australia (Harrington and Sanderson, 1994; Russell-Smith et al., 2004)."

Added to these Australian findings, we note that in a recent review of the scientific literature Lewis (2006) reports that most other tropical forests around the world also experienced significant increases in productivity over the last several decades; and he too concludes that the ongoing rise in the air's CO2 concentration is likely the key factor responsible for their increased robustness. Hence, it would appear that wherever one looks around this amazing planet of ours, the greening of the earth continues, which is our optimistic mantra.

Sherwood, Keith and Craig Idso

Banfai, D.S. and Bowman, D.M.J.S. 2006. Forty years of lowland monsoon rainforest expansion in Kakadu national Park, Northern Australia. Biological Conservation 131: 553-565.

Bowman, D.M.J.S., McIntyre, D. and Brook, B.W. In press. Is the Carpentarian Rock-rat (Zyzomys palatalis) critically endangered? Pacific Conservation Biology.

Bowman, D.M.J.S., Walsh, A. and Milne, D.J. 2001. Forest expansion and grassland contraction within a Eucalyptus savanna matrix between 1941 and 1994 at Litchfield National Park in the Australian monsoon tropics. Global Ecology and Biogeography 10: 535-548.

Harrington, G.N. and Sanderson, K.D. 1994. Recent contraction of wet sclerophyll forest in the wet tropics of Queensland due to invasion by rainforest. Pacific Conservation Biology 1: 319-327.

Lewis, S.L. 2006. Tropical forests and the changing earth system. Philosophical Transactions of the Royal Society B 361: 195-210.

Russell-Smith, J., Stanton, P.J., Edwards, A.C. and Whitehead, P.J. 2004. Rain forest invasion of eucalypt-dominated woodland savanna, Iron Range, north-eastern Australia: II. Rates of landscape change. Journal of Biogeography 31: 1305-1316.