Seizing resilience windows to foster passive recovery in the forest-water interface in Amazonian lands

Timing since deforestation for pastures implementation in the western Amazon: Impacts on stream water biogeochemistry

Water quality degradation is a global concern and land use changes is one of the main causes of water pollution globally. In the Brazilian Amazon, large-scale deforestation is mostly associated to pasturelands, with strong implications for soils and stream waters biogeochemistry and resulting in environmental degradation. Studies addressing soil biogeochemistry in Amazonian pastures of different ages documented a consistent pattern of elements peaking on the first years after deforestation, followed by a continuous decrease until reach depletion in older, degraded pastures. The same pattern is expected on the adjacent stream water biogeochemistry due to the land-water connection; however, this issue has not being explored. We assessed how timing since deforestation impacts water biogeochemistry in streams of Rondônia State, Brazil, a region that showed a relatively fast colonization process associated to large-scale deforestation for pasture implementation since 1970. Mapping deforestation from 1984 to 2011 and collecting water samples in 2012 for 41 headwater catchments, we (i) compared water biogeochemistry among streams draining undisturbed catchments with primary forests (PRI) and streams draining pasture catchments deforested mostly in a recent (NEW) and in a distant past (OLD); and (ii) related water biogeochemistry with land use intensity (pasture permanency along years), also considering the effect of covariates (soils, forest cover, and catchment area) in our analysis. Our results indicate that pasture implementation altered the concentrations of ions and nutrients in the stream ecosystem, with distinct water quality impacts between newer and older pastures. In general, the longer the area stayed under pasture use, the larger were the alterations in the water biogeochemistry (lower NO3-, DOC, and DOX and higher Ca2+, Mg2+, DIC and COND). Pasture degradation is a widespread process in the Amazon and it is strongly associated to increasing deforestation. Thus, pasture reclamation and intensification is urgently necessary to achieve the long-term productivity and sustainability of Amazonian pasturelands, avoiding new deforestation and environmental degradation. Adopting Best Management Practices (riparian forested buffers) is another action to protect water resources in the region.

Forest restoration improves habitat and water quality in tropical streams: A multiscale landscape assessment

Forest restoration has been a common practice to safeguard water quality and stream health but it is unclear to which extent and pace forest restoration recovers stream ecosystem structure and functions. Also, stream health might be affected by the forest restoration type and the quality of the interventions. Here, we sought to evaluate the recovery of stream habitat and water quality through forest restoration in catchments dominated by pasturelands, and explored the relationship between landscape structure and stream ecosystem recovery. We sampled a total of 30 catchments during the dry season of 2023, covering six different classes (five catchment per class), based on the type and extent of forest cover: (i) all catchment area covered by native forest remnants, (ii) catchments mostly covered by old (26-37 years) restored forests, (iii) catchments mostly covered by young (5-25 years) restored forests, (iv) catchments in a pasture matrix with forest remnants around springs, (v) catchments in a pasture matrix with riparian buffers covered by pioneer vegetation (mostly herbs and shrubs), and (vi) catchments mostly covered by pastures. Data on stream water (e.g. temperature, nutrients and sediments) and habitat (e.g. substrate heterogeneity and volume of wood debris) quality were sampled and landscape metrics calculated by GIS at reach, riparian and catchment scales. In catchments covered by remnant and old restored forests, the water temperature and nutrient concentration were lower, and instream leaf banks were higher, whereas the number of large wood debris was higher in forest remnant catchments. Water temperature and ammoniacal-N correlated with Normalized Difference Vegetation Index (NDVI) at reach scale. Substrate heterogeneity and volume of woody debris correlated strongly with NDVI and proportion of forest over 38 years old at the catchment scale. This outcome shows the potential application of forest structure (NDVI) and age for monitoring the stream ecosystem benefits of forest restoration. Overall, we found a gradient of recovery of both water and habitat quality progressing from more degraded (pasture-dominated catchments, pasture-dominated with forest remnants around springs, pasture-dominated with pioneer vegetation in riparian buffers) to more conserved catchments (young forest restoration, old forest restoration and old-growth conserved forests). In conclusion, the Atlantic Forest restoration contributed to improve water and habitat quality in streams, however these benefits were dependent on forest restoration age, extension and location.

The loss of riparian vegetation along streams causes morphological divergences in functional traits of semiaquatic insects (Heteropteran: Gerromorpha) in the eastern Amazon

Understanding the effects of mining activities on Amazonian streams and their impact on aquatic communities is of paramount importance in the current context of resource overexploitation in society. In this study, we assessed the significance of the environment and interspecific interactions on the organization patterns of semiaquatic insect species in a mineral extraction region in the eastern Amazon. We utilized the morpho functional characteristics of 22 species from the suborder Gerromorpha (Heteropteran), considering both the abundance and sexual dimorphism of these species. Additionally, we quantified the density of riparian vegetation surrounding each stream to categorize sampling points and evaluate whether there are differences in species distribution patterns among categories. We sampled 16 sites, categorized into two treatments based on the percentage of riparian vegetation in forested and deforested areas located in the Capim River Basin. We did not find the action of environmental filters on the total assembly; however, we found significant morphological divergence for all the traits analyzed. On the other hand, the separation of streams into treatments with different portions of riparian vegetation showed that there are significant differences between them regarding species distribution patterns. Forested streams within a 500-m radius have species distributed over a larger area, indicating that these streams have greater resource availability or that species can use these resources more efficiently. Our results demonstrate the importance of riparian vegetation for the studied communities, as well as for mitigating the impacts caused by mining activities.

Biological mechanisms matter in contemporary wildlife conservation

Given limited resources for wildlife conservation paired with an urgency to halt declines and rebuild populations, it is imperative that management actions are tactical and effective. Mechanisms are about how a system works and can inform threat identification and mitigation such that conservation actions that work can be identified. Here, we call for a more mechanistic approach to wildlife conservation and management where behavioral and physiological tools and knowledge are used to characterize drivers of decline, identify environmental thresholds, reveal strategies that would restore populations, and prioritize conservation actions. With a growing toolbox for doing mechanistic conservation research as well as a suite of decision-support tools (e.g., mechanistic models), the time is now to fully embrace the concept that mechanisms matter in conservation ensuring that management actions are tactical and focus on actions that have the potential to directly benefit and restore wildlife populations.