A new study by Ingmar R. Staude et al. calls for more restrictive policies around land use change in South Brazil’s grasslands. Read the full article, Local biodiversity erosion in south Brazilian grasslands under moderate levels of landscape habitat loss in Journal of Applied Ecology.

Common perception of biodiversity in Brazil is mostly biased towards the exotic wilderness of Amazonia, to lush rainforests that harbor species of all shapes and colors. From the plentitude of Brazil’s biomes, it’s the forest ecosystems and their rapid degradation that have caught attention from the world’s society and sparked a debate on conservation. A gradually emerging awareness of what is at risk has resulted in more sustainable land-use policies, even though deforestation of the Amazon continues to be a major problem.

Less attention has been paid to Brazil’s non-forest ecosystems. In particular, the South Brazilian grasslands, which stretch over two biomes in Brazil and jointly with the plains of Argentina and Uruguay form one of the largest temperate grassland extension on Earth, continue to be neglected in national conservation, but also in international efforts.

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Brazil’s southern grasslands have been suppressed by agricultural and forestry expansion. Photos: B.O. Andrade

Brazil’s southern grasslands harbor a wealth of biodiversity, a silent universe of grassland plants, homogeneous at first glance but with high biodiversity on all scales when looked at more closely. Who would think that in a square meter of these grasslands up to 56 plant species can be found? Rather unnoticed, these ecosystems have been and are still being converted to agriculture at a staggering pace. In about three decades, 50% of Brazil’s southern grasslands have been suppressed, making it the ecosystem with the highest Conservation Risk Index in Brazil. To date, there is little empirical evidence for the effects of habitat loss on these grasslands’ biological diversity, undermining any efficient conservation strategy or evidence-based management decision.

Not surprisingly, when native habitat is converted, multispecies assemblages are replaced by monocultures, which leads to biodiversity losses at the local scale. And if a certain species only occurred where now agriculture took over, this species may be lost forever. However, diversity loss may even proceed in unaltered remnants of primary habitats through indirect effects. The article “Local biodiversity erosion in South Brazilian grasslands under moderate levels of landscape habitat loss”, by Ingmar Staude and co-authors from the Universidade Federal do Rio Grande do Sul (UFRGS), in Porto Alegre, Brazil, is the first to show impact of reduction of overall grassland area on remnant grassland patches.

Importantly, the study was conducted in regions where habitat loss is far from extreme: the landscapes where the study was conducted all showed more than 50% of natural habitats. Nonetheless, the study evidenced that local plant species richness in grassland remnants decreased with increase of other land use types, that grasslands patches showed increasing biotic homogenization and that phylogenetic diversity also was reduced. The study additionally evaluated the response of ants, as an omnivore group with high levels of plant associations and found that ants responded to plant phylogenetic diversity. Ant generic richness declined up to 50% in plant communities with lowest phylogenetic diversity.

These findings suggests that biodiversity losses can occur at levels of habitat loss much below those commonly cited to have severe effects (e.g. 30%) and most importantly that the biological diversity of South Brazilian grasslands, both at the producer and consumer level, is at risk under the current rate of native grassland suppression. The authors caution that with the loss of evolutionary information ecosystem resilience may be affected too.

To avoid substantial losses of high biological diversity within this grasslands, and to prevent a state from which biodiversity cannot be restored anymore, efficient conservation, e.g. a higher protected area coverage and more restrictive policies for conversion of native grasslands to different land uses in South Brazil are urgent. Most importantly, the importance of biodiversity conservation in Brazil’s non-forest ecosystems has to be recognized by the public, policymakers and stakeholders.

Read the full article, Local biodiversity erosion in south Brazilian grasslands under moderate levels of landscape habitat loss in Journal of Applied Ecology.