Forests less affected by natural disasters and human action over millennia of evolution may paradoxically become the ones that concentrate the most vulnerable species to current destruction. Such forests are concentrated in the tropics and include the rainforest and the Amazon, says a new study.
The cruel logic behind the findings, described in the latest issue of the journal Science by an international team of scientists with the participation of several Brazilians, has to do with the concept of “extinction filters”.
According to this hypothesis, species exposed to severe threats during their evolutionary past would eventually become less susceptible to succumbing to new challenges such as habitat loss — so they would already have gone through an “extinction filter” and survived. On the other hand, animals and plants that have always lived in very stable environments would be relatively defenseless with the sudden and intense arrival of such threats.
The study group, which includes researchers such as Brazilian biologist Cristina Banks-Leite of Imperial College London, tested this hypothesis by analyzing a database of information on 4,489 animal species from around the world, including arthropods (group including insects), birds and mammals, among others.
They cross-linked information on the geographic distribution of critters with data on the incidence of severe storms (such as Caribbean hurricanes), the presence of glaciers, large natural fires and historical cases of large-scale deforestation (with more than 50% loss). vegetation cover).
Another crucial factor taken into account by the team is forest fragmentation and the relationship of each species with this variable. As the name suggests, very fragmented habitats are those that have been devastated to such an extent that only isolated and relatively small patches of forest are left, often surrounded by what ecologists call the 'matrix' (usually agricultural areas or in some cases , urban).
Under these conditions, some more versatile species can do well by "jumping" from one forest fragment to another across the matrix or even adapting to life in it. Other species, however, need large areas of continuous forest to maintain and do not get along with the remaining fragments, and can not cross the matrix.
It turns out that by matching the data on geographic distribution of animals and the long-term threats in each environment with the habitat type of the species, a pattern appeared relatively clearly. In regions of the planet with a high degree of disturbance due to natural factors and human action, versatile species predominate, which turn out well both in the heart of the forest and on the edge of forest fragments or even in the matrix.
In such regions, species that rely solely on an intact forest core are 80% less common. Already in the relatively undisturbed regions of the earth throughout history, 51.3% of species tend to avoid edges of fragments or the matrix, being found preferably in the deepest parts of the forest.
That is, the data suggest that there is a predominance of such “demanding” species in forests that, throughout their evolutionary history, seem to have suffered less disturbance. Such animals would therefore have more difficulty adapting to more degraded and human-fragmented environments, which are concentrated in tropical regions of the Americas, Africa, and Southeast Asia – precisely those most targeted by the momentum of deforesters in recent decades.
The news may be especially bad for the Brazilian rainforest. Most of what is left of the biome – less than 30% of its original cover – is restricted to small forest fragments of less than 10 hectares. To avoid rapid erosion of the biodiversity of this and other biomes, it will be necessary to invest in ecological corridors that connect fragments to each other, for example.
Among the Brazilian authors of the study are also researchers from UFMS (Federal University of Mato Grosso do Sul), Federal University of Lavras (MG) and Santa Cruz State University (BA), as well as other institutions.
(tagsToTranslate) amazonia (t) Atlantic Forest (t) deforestation (t) zero deforestation (t) reforestation (t) environment (t) leaf