Biogeography and conservation in Southeast Asia

Two groups of papers are lumped in this theme. First, are a series of papers on the little studied biogeographic transition between the Indochinese and Sundaic biotas. The biotas are significantly different from one another but the history of their differentiation is not understood. Second, are several papers on the impacts of humans and global climate change on biogeography and conservation in Southeast Asia.

Origins of today's biogeographic patterns

A.R. Wallace (1876) noted that there was a transition between the Indochinese fauna of Asia proper and that of the Indo-Malay region near the northern end of the Thai-Malay peninsula. Plant geographers subsequently noted a transition in the plants and van Steenis (1950) showed that this boundary was more significant (involving 575 genera) than that associated with Wallace’s line separating the floras of Asia and Australia. Surprisingly, this biogeographic transition has been almost completely ignored. I published four papers in 2003 aimed at drawing attention to this little investigated feature. One concerns the Sundaland-Asian faunal transition of the resident rainforest bird species which I showed lies near the Isthmus of Kra. Although the transition is well-known to local naturalists it had never been formally documented or analyzed. In 1995 an undergraduate, Jennifer Hughes, and I analyzed a very large avian distributional dataset assembled by my colleague Phil Round in Thailand. We were able to show that an alleged biogeographic turnover was truly significant (Publication 208). The reason why the faunal transition occurs in the northern part of the peninsula and not 500 km further south where the floral transition lies is puzzling. I offer one explanation in terms of hypothetical Miocene and Pliocene marine transgressions in the companion manuscript (Publication 207). I used the revised global eustatic curve based on unpublished oil and gas exploration data to show how the Malay peninsula may have been breached twice for long enough for species or generic level faunal differentiation to occur. This second paper has been widely cited by biologists working on patterns in other parts of the world which may have had similar histories. A third paper reported the detailed avian distributional data (Publication 212), and a fourth discussed the paradox presented by the apparent non-congruence of the faunal and floral transitions (Publication 211).

Two years after the above papers were published it became clear that the underpinning sea level curve, the Vail/Haq or Exxon curve, was seriously flawed. My use of that curve to postulate the marine transgressions was based on nearly 30-years of use by a large number of workers. Nevertheless, Miller (2005, published in Science) showed that the proposed marine high stands and transgressions had not occurred. This necessitated that I either retract my hypothesis or replace it with a better one; I chose the latter. In the context of the first analysis of the biogeographic transition in mammals I offered a new hypothesis based on the revised global sea level curve to explain (1) the position of the transition in the northern Thai-Malay peninsula and (2) the curious (and previously unrecognized) 30% reduction in mammal species diversity associated with the transition. It is still to early to tell what impact Publication 222 will have, but early indications are favorable. Follow-on grant proposals to the NSF for funds to study mammal species niche conservatism across the transition using stable isotopes have not yet been funded. Currently, I am re-analyzing the avifaunal distributional data based on the availability of a new monograph on Malay passerines (Manuscript C13).

These activities have led to my being asked to serve as the external examiner of three Australian PhD theses on the phylogeography of Southeast Asian mammals, snakehead fish and giant freshwater prawns.

Global change and its impact on natural and human ecosystems in Southeast Asia

It is not possible to conduct biological fieldwork in Southeast Asia without getting caught up in regional environmental battles. Development, human rights and wildlife conservation are inseparably linked. My early studies of disease transmitting snails in the Mekong River led to my involvement in the battle to prevent the construction of a hydropower dam on a tributary in Thailand (Publication 134, testimony presented at The World Bank, invited plenary lecture in Thailand (Publication 150)). Subsequently, I have begun to draw attention to the likely catastrophic consequences of Chinese dams on the mainstream of the Mekong (Publication 221). Similarly, my interest in Pleistocene sea level changes led to two papers on the consequences of the on-going sea level rise in Southeast Asia; the impacts will be profound for both humans and wildlife (Publications 220, 223). I have also been asked to comment on the sustainability of hill tribe swidden agriculture in the hills of northern Thailand (publication 196). Rapid regional development is occurring with minimal concern for the environmental consequences and will clearly lessen the region’s sustainability for centuries to come. As a visiting researcher I have tried to provide ecological counsel when asked to do so.

Publications

134. Woodruff, D.S. Scientific aspects of sustainable development: Environmental assessment of dams and reservoirs. [In Thai]. Kasetsart University Journal of Science 10(1):56–57. (1992n).
Note: This is the only report, to date, arising from my involvement in an international fight to stop the construction of the Pak Mun Dam in Thailand. Thai academics were muzzled by their own government so it fell to a small group of foreigners to argue the case at The World Bank. Although the EIS was seriously flawed, the irreversible damage to a freshwater biodiversity hotspot was found to be irrelevant. The WB was, however, forced to abide by its own policy of transparency and for the first time in history environmentalists won a split vote of the Directors, the secret EIS was released, and Thai scientists won the right to comment on their government’s environmental policy.

196. Woodruff, D.S. Sustainable agriculture and biodiversity conservation. In: 2nd Asia-Pacific Conference on Sustainable Agriculture. Phitsanulok, Thailand, October 18-20, 1999, pp. 55–62. (2001b).
Note: Discusses the sustainability of swidden agriculture as practiced by some hill-tribes in the remaining forests of north Thailand. Recent gazetting of these forests as national parks has created additional problems for these people as the Thai government has not afforded them protection as citizens or land rights. The recent immigration of refugees (other hill-tribes) and lowland Thais into the hills further complicates the situation. Re-forestation and watershed management are necessary to improve downstream water quality but this cannot be achieved until hill-tribes are afforded basic social rights. Sustainable agriculture in this area will have to be based on intensified cultivation rather than further land conversion.

207. Woodruff, D.S. Neogene marine transgressions, paleogeography and biogeographic transitions on the Thai Malay Peninsula. Journal of Biogeography 30:551–567. (2003a).
Note: Evidence suggests that the Thai-Malay peninsula was cut by seaways for a million years in the Pliocene and for longer in the Miocene. These heretofore unrecognized barriers to dispersal may have permitted the differentiation of the Indomalay biota from the Indochinese biota and account for the position of the great biogeographic transition on the peninsula today. Publications 206, 209, 210 and 222 are companion papers. [No. of citations: 63]

208. Hughes, J.B., P.D. Round and D.S. Woodruff. The Indochinese-Sundaic faunal transition at the Isthmus of Kra: an analysis of resident forest bird species distributions. Journal of Biogeography 30:569–580. (2003b).
Note: This report provides the first documentation of a faunal transition recognized by Wallace but never subsequently documented or analyzed. The bird distributional records were assembled by ornithologist Phil Round and the analysis was conducted with Jennifer Hughes, an undergraduate. [No. of citations: 38]

211. Woodruff, D.S. The location of the Indochinese-Sundaic biogeographic transition in plants and birds. Natural History Bulletin of the Siam Society 51:97–108. (2003e).
Note: I discuss the paradox presented by my observation that the avifaunal transition appears to lie 500 km north of the floral transition as defined in 1950 by van Steenis.

212. Round, P.D., J.B. Hughes and D.S. Woodruff. Latitudinal range limits of resident forest birds in Thailand and Indochinese-Sundaic Zoogeographic transition. Natural History Bulletin of the Siam Society 51:69–96. (2003f).
Note: This paper provides the distributional data for about 545 forest associated bird species summarized in Publication 208. [No. of citations: 7]

221. Woodruff, D.S. International impacts of damming the Mekong River. In: Global Perspectives on Large Dams. Evaluating the State of Large Dam Construction and Decommissioning across the World. DiFrancesco, K. and K. Woodruff, eds. Yale School of Forestry & Environmental Studies, Report no. 13: 85–89. Yale University, New Haven. (2008).
Note: This paper describes the cascade of dams constructed or under construction on the Langcan (Mekong) river in Yunnan, China, and their ecological effects on downstream communities. The nature of the probable eco-catastrophes at the level of the Tonle Sap, Cambodia, and the Mekong delta, Vietnam, are outlined.

222. Woodruff, D.S. & Turner, L.M. The Indochinese–Sundaic faunal transition: an analysis of terrestrial mammal species distributions. Journal of Biogeography 36:803–821. (2009).
Note: Like the above papers on bird distribution patterns this was the first systematic study of the geographic ranges of all Southeast Asian mammals; 325 species over a 2,000 km transect. We reported of the discovery of the species diversity anomaly in the northern peninsula and presented the first biogeographic analysis based on the new global sea level curve. [No. of citations: 7]

220. Woodruff, D.S. and Woodruff, K.A. Paleogeography, global sea level changes, and the future coastline of Thailand. Natural History Bulletin of the Siam Society 56: 1–24. (2008).
Note. This is the first widely read report on past and future sea level changes focused specifically on Thailand. It is written for government officials, academics and policy makers to draw attention to the literature, current understanding of the facts, and the projections for sea level rise in the next 300 years. We present satellite-data based maps to illustrate the impact of +2, +25 and +50 m sea level rises. [No. of citations: journal not monitored]

223. Woodruff, D.S. Biogeography and conservation in Southeast Asia: how 2.7 million years of repeated environmental fluctuations affect today's patterns and the future of the remaining refugial-phase biodiversity. Biodiversity and Conservation 19: 919–941. (2010) Published online: DOI 10.1007/s10531–010–9783–3
Note: The purpose of this paper was to bring together the insights learned from my detailed studies of birds and mammals and generalize them to the entire biota of Southeast Asia. I offer a new interpretation of the region’s Neogene biogeographic history based on the revised global sea level curve. I conclude that today’s patterns, and not those of the glacial maximum, are compressed or refugial and that projected sea level and climate changes will have very significant negative impacts on humans and wildlife. [No. of citations: 46]

C13. Woodruff, D.S. Grey, R. The Indochinese-Sundaic avifaunal transition. Journal of Biogeography in preparation.
Note: The publication of David Wells’ Birds of the Malay Peninsula volume 2 and the correction of the global sea level curve necessitate a revision of the analysis presented in publications 208, 212. The distributional data have been re-coded and are being verified by Wells and Round. It is too early to tell whether the interpretive conclusions reached in the earlier study will stand and/or whether the birds also show a species diversity anomaly similar to that we discovered subsequently in the non-marine mammals.

Global sea level curve over the last 10 Myr and the impact of +2m and +25m sea level rises on Southeast Asian shorelines (Publications 220, 222, 223). In the 30-million year sea level curve (inset) the dotted line is the old Exxon/Vail/Haq/Vail curve that was used in Publications 207, 208, 211 & 212 but is now recognized as flawed and corrected in my later papers.