Increasing research on the flora of the Tapajós basin is critical for at least three reasons. First, the flora is very poorly known, and many large areas within the basin are unrepresented by collections in herbaria. Models of plant diversity in the region are thus based on gross extrapolations from relatively few data points. This paucity of critical data impedes research and limits the extent to which considerations about plant diversity inform development, management, and conservation decisions.
Second, although the data are scarce, there is good reason to suspect that the flora is highly diverse and unique. Our preliminary plot-based sampling suggests that select forests of the lower and middle Tapajós basin have only slightly fewer species than the the most hyper-diverse forests of western Amazonia, which are the most species-rich forests on earth. Moreover, ongoing collecting in the Basin is turning up many new records of species for the region, and even a number of species that are entirely new to science. Finally, the regions’ complex geological history and unusual climate, which is more highly seasonal than in other parts of Amazonia, causes us to suspect that the percentage of endemism (i.e., uniqueness) in the flora is underappreciated, and indeed the list of species that are known only from the Basin is growing.
Third, the Tapajós Basin is undoubtedly among the parts of the Amazon under the highest levels of ecological threat from human-induced habitat destruction. The region is criss-crossed by two major roads, the Santarém-Cuiabá road (BR-163) and the Trans-Amazonian Highway (BR-230). When these roads opened in the 1970s, they exposed large areas of Amazonian wilderness to settlement and exploitation. Since that time, the proliferation of satellite roads and roadside settlements, along with the expansion of urban areas, has been accompanied by the conversion of huge areas of forest to pasture. Sprawling deforestation near cities and along the major road systems is now readily apparent in satellite images of the Basin and has had the affect of fragmenting the remaining blocks of forest. Other mounting threats to natural ecosystems in the Basin include poorly controlled logging and mining activities, increasing drought and wild fire, which may be associated with human-induced climate change, planned large-scale hydroelectric development on the Tapajós River and its major tributaries, the northward march of the soybean cultivation frontier, political and social conflict, and a general lawlessness that prevails in some areas.
While the Brazilian government has created a large number of conservation units in the region, the majority are underfunded and understaffed; thus the extent to which they provide long-term refuges for biodiversity is questionable. As the region undergoes rapid and probably irreversible ecological change in the coming years, it seems likely that a substantial percentage of the indigenous biodiversity will be lost before it can be scientifically documented.
