99% of Caatinga biome could lose plant species due to climate change: Study

An unprecedented study analyzed 420,000 occurrence records for 3,060 Caatinga plant species and concluded that 99% of the plant communities there are expected to lose species by 2060.Even though the species in the biome are theoretically adapted to extreme climates, researchers found that the Caatinga is much more vulnerable to climate changes than previously believed.Protecting the more sensitive areas and restoring landscape vegetation connectivity is crucial for the resilience of Caatinga ecosystems; the biome is one of Brazil’s least protected, as less than 9% of its area lies within Conservation Units.

The Amazon Rainforest — together with other forests around the globe — lies at the center of concern over climate changes inside Brazil and worldwide. Yet little is studied and even less said about the dry, hot tropical biomes like the Caatinga, which occupies around 800,000 square kilometers (310,000 square miles, roughly the size of Mozambique) in mostly Northeastern Brazil. But this is beginning to change.

Researchers from the federal universities of Paraíba (UFPB), Pernambuco (UFPE) and Viçosa (UFV); from Campinas State University (UNICAMP) and Goiano Federal Institute (IFG) carried out a study in which they concluded that 99% of the Caatinga’s plant communities will lose species by 2060, resulting in a 40% simplification of the region’s plant type composition.

Data from hundreds of scientific herbarium collections, together with the literature, were analyzed to produce an unprecedented data bank with some 420,000 records of occurrence for 3,060 plant species in the biome.

“These data were complemented by the growth form of each species, which specifies if the plant is a tree, a bush, an herbaceous perennial, a succulent, an herb or a vine,” says UNICAMP biologist Mario Ribeiro de Moura, the study’s main author.

The second step involved building statistical and AI models allowing the researchers to map out geographic distribution of plants in the Caatinga, not only for the present time but also for different climate change scenarios in the future. “This sort of approach makes it possible to come to a consensus between the scenarios we tested,” explains Moura. “In other words, we were able to understand which regions showed similar results in all the models and which showed marked differences.”

Caatinga vegetation in the municipality of Sento Sé, Bahia. Photo by Willianilson Pessoa.

According to Moura, when these projections are applied to all the species, it is possible to evaluate how climate changes may affect plant community richness, composition and structure. Richness refers to the number of species found there, while composition refers to which plant species are represented in the community. Structure speaks to the proportion of species of each type of growth form — in other words, if the group has more arboreal or non-arboreal plants

According to Moura, climate change is expected in general to cause arboreal and rare species to be substituted by non-arboreal and generalist species, as these are found in many different regions of the biome. “This sort of change in vegetation structure can cause a drop in ecosystem services like the production of plant biomass and carbon capture,” he warns

Moura also explains that plants store carbon from the atmosphere during photosynthesis so they can grow branches, roots and leaves while releasing oxygen. “These ecosystem services are called carbon storage and sequestering, respectively. A reduction in the number of trees will reduce the volume of these services, further worsening the climate crisis.”

More vulnerable than once imagined

IFG biologist Daniel de Paiva Silva, who also participated in the study, says he believes the results their team found are “neuralgic” in relation to climate changes. “Naturally, Caatinga species are adapted to the extreme temperature conditions that occur in the biome,” he explains. “Finding this result in plants that are, in theory, more ‘climatically protected from and adapted to’ extreme temperatures and climates raises concern about communities of plant species in other biomes, which will be just as affected by climate changes, but which are less adapted to extreme climates like those in the Caatinga.”

In other words, this study enabled researchers to conclude that, even though it is a biome with species theoretically adapted to extreme climates, the Caatinga is much more vulnerable to climate changes than expected. “If a region with species adapted to such climates will be significantly affected on the short term, it gives rise to concern over other Brazilian biomes with plant communities unprepared and unadapted to global warming like Amazonia, the Atlantic Rainforest and the Pantanal, where conditions are much milder,” explains Silva.

A mandacaru flower (Cereus jamacaru). Photo courtesy of Mauricio Mercadante via Flickr (CC BY-NC-SA 2.0).

Moura says this study was different than others because the team created a model structure to provide more robust projections by minimizing problems related to the uncertainty of climate projections, limitations of species dispersion and its applicability to future scenarios. “The approach we used synthesizes over 1 million projections of the possible responses that 3,060 plant species may have to climate changes,” he explains. “This multitude of scenarios and evaluations aims to provide the best projections possible, together with the uncertainties associated with them [to map out the locations where the forecasts are solid].”

UNICAMP biologist and zoologist Thaís Guedes, who was not on the research team, says he believes the study’s results serve as yet another warning to government leaders and society: The topic of climate change must be addressed, and serious, long-term planning created, if the dry tropical forests of the Caatinga are to be kept alive.

“The data show how urgent it is that we think of effective actions to preserve Brazilian biodiversity in a world that is undergoing change, either with the impacts of climate changes or of landscapes due to other human activities like mining, agribusiness and wildfires,” states Guedes.

Caatinga landscape in the state of Rio Grande do Norte. Photo courtesy of Willianilson Pessoa.

Guedes also calls attention to another issue. “Even though this study was carried out on plants, the results show that the landscape will undergo significant change — that it will lose its heterogenic nature and become more homogenic. As a zoologist who studies the reptiles and amphibians in the region, I find the results very worrisome because I believe this homogenization of vegetation will have a snowball effect and bring about the loss of fauna species as well.”

This is why, according to Moura, the study’s results show how protecting more sensitive regions and restoring landscape vegetation connectivity is crucial for the resilience of Caatinga ecosystems. “It is urgent that we create conservation and forestry management policies at the municipal, state and federal levels. Involving local communities and natural resource stakeholders in the Caatinga is vital for these initiatives to become successful.” It is important to remind ourselves that the biome is one of Brazil’s least protected: Less than 9% of the area lies within Conservation Units.

 
Banner image: A facheiro cactus (Pilosocereus pachycladus) in Pedra da Boca State Park, Paraíba. Photo by Carla Belke via Wikimedia Commons (CC BY-SA 4.0).

Citation:
Moura, M. R., Nascimento, F. A., Paolucci, L. N., Silva, D. P., & Santos, B. A. (2023). Pervasive impacts of climate change on the woodiness and ecological generalism of dry forest plant assemblages. Journal of Ecology. Retrieved from https://doi.org/10.1111/1365-2745.14139

 
This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on Sept. 6, 2023.

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