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Research Highlights: We find that biochar plus fertilizer has synergistic and positive effects on seedling growth and robustness, but slightly lowers early seedling survival. Biochar plus fertilizer has the potential to greatly decrease costs associated with afforestation as compared to traditional fertilization and gives better results. Background and Objectives: Biochar can improve soil fertility and plant yield in crops. However, there is little information regarding the effects of biochar on trees, even though reforestation/afforestation projects are increasing and are often unsuccessful due to soil fertility limitations. This study aims to increase knowledge of biochar use as a reforestation tool. Materials and Methods: We measured survival and growth in an early ((Guazuma crinita Mart. [n = 240])) and a late (Terminalia amazonia (J.F. Gmel.) Exell. [n = 240]) successional species under 6 different biochar treatments in a 6-month nursery experiment. Results: (i) Survival was highest in the 1 t/ha biochar treatment, while treatments containing fertilizers or biochar at 5 t/ha lowered the survival rate of both species compared to the control; (ii) simultaneous addition of biochar and fertilizer lead to significant increases in height, diameter, total number of leaves, and aboveground and belowground biomass of both species as compared to other treatments; (iii) biochar treatment containing 1 t/ha with and without fertilizer showed significantly better results than applications of 5 t/ha; and (iv) Guazuma crinita responded more strongly to treatments containing biochar and fertilizers compared to Terminalia amazonia, which is suggestive of greater synergetic effects of biochar and fertilizer addition on early successional tree species. Conclusions: Applying biochar and fertilizer is synergistic and outperforms any single treatment, as well as the control, in terms of plant performance. This case study suggests that biochar can greatly improve reforestation/afforestation projects by increasing plant performance while substantially reducing fertilizer and labor maintenance costs. Field experiments and testing of additional species is needed to generalize the findings.

Worldwide demand for gold has caused increased extractive activities in the Western Amazon, resulting in a wide-scale transformation of the Madre de Dios river basin (Peru) due to Artisanal and Small-scale Gold Mining (ASGM). These impactful activities profoundly affect the natural landscape and hydroscape as terra firme forest and floodplain habitats are deforested leaving a vast landscape of abandoned ponds that are subsequently colonized from surrounding water bodies. However, the metacommunity dynamics of these emergent networks of connected wetlands and their environmental drivers remain virtually unknown. Here, we present a one-year (May 2017–May 2018) study conducted to assess the composition, abundance and trophic structure of fish assemblages in three abandoned ASGM ponds and their interactions in relation to those of other freshwater groups (macroinvertebrates, phytoplankton and zooplankton). We aimed to determine the influence of environmental parameters on community composition, focused on flood pulse influence (FPI), seasonality, and to identify indicators for predicting aquatic communities’ assemblages. A remarkably abundance and diversity were found totaling 4601 sampled fish from 6 orders, 27 families, 68 genera and 103 species, as well as 87 macoinvertebrate, 71 phytoplankton and 44 zooplankton taxa. The two FPI ponds showed a more stable fish trophic structure throughout the year than the unique non-FPI, probably due to the floods provision of buffer against the lack of resources that occurs during the dry season. Conversely, fish of higher trophic levels were not detected during the dry and transition-to-wet seasons in the non-FPI pond surveyed. Community trajectory analysis showed greater stability of fish assemblages in the non-FPI pond compared to the FPI ponds, which experienced larger disturbance of environmental parameters and biotic inputs during flooding events. Detrended correspondence analysis showed floods as the key factor influencing aquatic communities and species accumulation. However, whereas floods had a large influence on fish and macroinvertebrates, seasonality was the main driver for plankton. FPI ponds showed six-fold higher fish and macroinvertebrate species richness than non-FPI ones, while plankton showed an opposite trend. FPI was the main factor determining the taxonomic composition of fish, followed by dissolved oxygen. Macroinvertebrates were also affected by FPI together with pH and the presence of grassed banks, while conductivity determined phytoplankton composition. Our study presents novel evidence on the highly heterogeneous communities of ASGM abandoned ponds, highlighting their important ecological value and potential role in providing of ecosystem services currently overlooked from conservation policies and management of the aquatic resources.

While deforestation rates decline globally they are rising in the Western Amazon. Artisanal-scale gold mining (ASGM) is a large cause of this deforestation and brings with it extensive environmental, social, governance, and public health impacts, including large carbon emissions and mercury pollution. Underlying ASGM is a broad network of factors that influence its growth, distribution, and practices such as poverty, flows of legal and illegal capital, conflicting governance, and global economic trends. Despite its central role in land use and land cover change in the Western Amazon and the severity of its social and environmental impacts, it is relatively poorly studied. While ASGM in Southeastern Peru has been quantified previously, doing so is difficult due to the heterogeneous nature of the resulting landscape. Using a novel approach to classify mining that relies on a fusion of CLASlite and the Global Forest Change dataset, two Landsat-based deforestation detection tools, we sought to quantify ASGM-caused deforestation in the period 1984–2017 in the southern Peruvian Amazon and examine trends in the geography, methods, and impacts of ASGM across that time. We identify nearly 100,000 ha of deforestation due to ASGM in the 34-year study period, an increase of 21% compared to previous estimates. Further, we find that 10% of that deforestation occurred in 2017, the highest annual amount of deforestation in the study period, with 53% occurring since 2011. Finally, we demonstrate that not all mining is created equal by examining key patterns and changes in ASGM activity and techniques through time and space. We discuss their connections with, and impacts on, socio-economic factors, such as land tenure, infrastructure, international markets, governance efforts, and social and environmental impacts.