Chronic anthropogenic disturbance drives the biological impoverishment of the Brazilian Caatinga vegetation

Abstract

Pernambuco, Av. Professor Moraes Rego s/n, Cidade Universit aria, CEP: 50670-901 Recife, Brasil Summary 1. In addition to acute transformations of ecosystems caused by deforestation, old-growth forests world-wide are being increasingly altered by low-intensity but chronic human disturbance. Overgrazing and the continuous extraction of forest products are important drivers of chronic disturbance, which can lead to the gradual local extinction of species and the alteration of vegetation structure. 2. We tested this hypothesis in the Brazilian Caatinga vegetation, one of the most speciesrich and populated semi-arid regions of the world. Using a multimodel averaging approach, we examined the impact of five recognized indicators of chronic disturbance (i.e. proximity to urban centre, houses, roads, density of people and livestock) on the diversity, abundance and evenness of 30 woody plant communities. We separately tested the response of seedlings, saplings and adults to identify the ontogenetic stages that are most susceptible to chronic disturbance. 3. We recorded over 11 000 individuals belonging to 51 plant species. As expected, most indicators of chronic disturbance were negatively related to species diversity and stem abundance, with a variable effect on community evenness. The density of people and density of livestock were the main factors driving changes in plant communities, with a stronger negative impact on seedling and sapling diversities. Species composition also varied significantly with disturbance indicators, irrespective of ontogeny. 4. Our results show the potential negative impact that chronic disturbance can have on Caatinga plant assemblages and highlight the fact that disturbance resulting from an extractivism-based and subsistence economy are probably driving old-growth forest stands towards shrub-dominated secondary stands. 5. Synthesis and applications. These findings indicate that chronic disturbance should not continue to be neglected and we argue for: (i) research and rural programmes able to support better practices in terms of land use and sustainable exploitation of forest resources, (ii) improved governance and law enforcement to shift extractivism towards sustainable standards, and (iii) expanding the coverage and effective implementation of strictly protected areas.

New records and update on the geographic distribution of Lontra longicaudis (Olfers, 1818) (Carnivora: Mustelidae) in Seasonally Dry Tropical Forests of northeastern Brazil

“…Considering only studies that present geographic coordinates, we report here the first accurate records of the species for five of the 10 river basins: Pium (RN), Jundiaí (RN), Jacu (RN), Curimatau (RN/PB), and Coruripe (AL) ( Table 1). Except for São Francisco River, all of the sampled river stretches have an intermittent hydrologic regime, maintaining some population, and has been under increasing anthropic pressure for years (Ribeiro et al 2015).…”

“…This is especially important in the Caatinga, a highly impacted biome that has been neglected by scientific research and conservation strategies (Santos et al 2011, Ribeiro et al 2015. Water, an essential resource for otters, is increasingly scarce and demanded by human population in this biome (Krol et al 2001).…”

Degradação e riscos à desertificação no Alto Curso do rio Paraíba - PB/Brasil

“…Neste sentido, nas três situações apresentadas em formas de mapas, a maior rarefação da caatinga encontra seu mais expressivo correspondente espacial nas proximidades dos corpos hídricos, particularmente no entorno dos maiores rios da região, com destaque para o rio Paraíba, além dos reservatórios de água, já que historicamente essas áreas favoreceram a prática de atividades agrícolas, pecuárias e extrativistas, além da concentração populacional, inclusive das cidades, acarretando as mudanças mais drásticas na vegetação presente originalmente. Logo, corroborando com Ribeiro et al (2015), os maiores contingentes de pessoas e gado tem sido os principais fatores de mudanças na composição vegetal, em quantidade e diversidade, com impacto negativo mais forte em plântulas, o que pode ser parcialmente visualizado nos mapas apresentados. Dessa forma, em um processo contínuo, temos um empobrecimento da vegetação que vai piorando ao longo do tempo, como consequência direta da presença das atividades antrópicas, além das consequências ligadas a ocorrência de estiagens prolongadas e sua influência nos remanescentes de cobertura vegetal.…”

“…Como consequência dessa situação, temos menor disponibilidade de sementes e também dos animais selvagens dispersores destas, visto que foram afugentados ou mesmo extintos, através da caça direta ou modificação intensa dos ambientes de onde tiravam a sua sobrevivência.Diante da menor cobertura vegetal e da renovação desta, a compactação dos solos, com capacidade naturalmente baixa de acúmulo de água no subsolo, fica ainda mais reduzida, afetando direta e negativamente os poucos remanescentes de espécies vegetais mais exigentes em água (SOUZA & MARTINS, 2012), criando ambientes de perturbação crônica (RIBEIRO et al, 2015).…”

Temporal evaluation of the Conservation Priority Index for medicinal plants

“…Chronic anthropogenic disturbances are continuous human actions of biomass removal from forest resources that have deleterious effects at population, community and ecosystem levels, but do not result in abrupt and complete environmental changes (Singh 1998;Martorell & Peters 2005). These disturbances, in turn, do not represent an immediate risk to plant populations, but they have the capacity to cause changes in the biology of species, altering reproduction rates and making it difficult to re-establish plant cover (Ribeiro et al 2015;Ribeiro-Neto et al 2016). Assuming that the studied environment is subjected to the direct influence of anthropic action and was totally devoid of conservation efforts over time, this study aims to infer the current conservation status of species considered as conservation priorities in the first study.…”