Most terrestrial ecosystems have lost megafaunal vertebrates (>44 kg) since the Pleistocene (from two million to 11 thousand years ago). The main practical justification for studying the consequences of large vertebrate extinctions is that they may provide a possible model for predicting the impacts of the on-going removal of the surviving megafauna—and numerous smaller species—from most of the tropics.

By consulting a large amount of literature, Prof. Richard T. Corlett of Xishuangbanna Tropical Botanical Garden (XTBG) assessed the likely impacts of prehistoric megafaunal losses in the lowland tropics and discussed potential conservation responses.

The review considered the environmental impacts—and modern-day implications for conservation management—of all tropical lowland extinctions of vertebrates >44 kg body mass from the early Middle Pleistocene (781,000 years ago), when most areas had a generally modern vertebrate fauna, to the Holocene (>2000 years ago, and thus before any recent ‘baseline’).

The review found that the most likely impacts included the co-extinction of parasites, a reduction in environmental heterogeneity, the release of competitors and prey (including plants), and a loss of quality and quantity in seed dispersal services.

However, much of the literature on those impacts is based on arguments by analogy with the extant megafauna, since the fossil and paleoenvironmental record is rarely, if ever, good enough to detect the expected impacts of megafaunal extinctions.

The scientist suggested that people should prioritize conservation and reintroduction of the surviving megafauna and need reversible experiments with taxon substitutes for extinct species. He also proposed that special conservation attention should be paid to megafaunal-dependent orphans and anachronisms.

The study entitled “The shifted baseline: Prehistoric defaunation in the tropics and its consequences for biodiversity conservation” has been published online in Biological Conservation, http://dx.doi.org/10.1016/j.biocon.2012.11.012