Impacts of logging roads on tropical forests

Threat of mining to African great apes

The rapid growth of clean energy technologies is driving a rising demand for critical minerals. In 2022 at the 15th Conference of the Parties to the Convention on Biological Diversity (COP15), seven major economies formed an alliance to enhance the sustainability of mining these essential decarbonization minerals. However, there is a scarcity of studies assessing the threat of mining to global biodiversity. By integrating a global mining dataset with great ape density distribution, we estimated the number of African great apes that spatially coincided with industrial mining projects. We show that up to one-third of Africa's great ape population faces mining-related risks. In West Africa in particular, numerous mining areas overlap with fragmented ape habitats, often in high-density ape regions. For 97% of mining areas, no ape survey data are available, underscoring the importance of increased accessibility to environmental data within the mining sector to facilitate research into the complex interactions between mining, climate, biodiversity, and sustainability.

Mapping roadless areas in regions with contrasting human footprint

In an increasingly human- and road-dominated world, the preservation of functional ecosystems has become highly relevant. While the negative ecological impacts of roads on ecosystems are numerous and well documented, roadless areas have been proposed as proxy for functional ecosystems. However, their potential remains underexplored, partly due to the incomplete mapping of roads. We assessed the accuracy of roadless areas identification using freely available road-data in two regions with contrasting levels of anthropogenic influence: boreal Canada and temperate Central Europe (Poland, Slovakia, Czechia, and Hungary). Within randomly selected circular plots (per region and country), we visually examined the completeness of road mapping using OpenStreetMap 2020 and assessed whether human influences affect mapping quality using four variables. In boreal Canada, roads were completely mapped in 3% of the plots, compared to 40% in Central Europe. Lower Human Footprint Index and road density values were related to greater incompleteness in road mapping. Roadless areas, defined as areas at least 1 km away from any road, covered 85% of the surface in boreal Canada (mean size ± s.d. = 272 ± 12,197 km2), compared to only 0.4% in temperate Central Europe (mean size ± s.d. = 0.6 ± 3.1 km2). By visually interpreting and manually adding unmapped roads in 30 randomly selected roadless areas from each study country, we observed a similar reduction in roadless surface in both Canada and Central Europe (27% vs 28%) when all roads were included. This study highlights the urgent need for improved road mapping techniques to support research on roadless areas as conservation targets and surrogates of functional ecosystems.

Protecting Life and Lung: Protected Areas affect fine particulate matter and respiratory hospitalizations in the Brazilian Amazon Biome

There is growing recognition of the connection between ecosystem conservation and human health. For example, protection of tropical forests can affect the spread of infectious diseases, water quality, and dietary diversity, while forest loss can have important consequences for respiratory health due to the use of fire for converting land to alternative uses in many countries. Studies demonstrating links between ecosystems and health often conclude with recommendations to expand policies that protect natural ecosystems. However, there is little empirical evidence on the extent to which conservation policies actually deliver health benefits when they are implemented in real contexts. We estimate the effects of protected areas (PAs), the dominant type of conservation policy, on hospitalizations for respiratory illness in the Brazilian Amazon biome. We find that doubling upwind PAs reduces PM2.5 by 10% and respiratory hospitalizations by 7% in the months of most active biomass burning. Brazil has an extensive network of PAs, but investments in management and enforcement have declined in recent years. Forest fires have increased dramatically over the same period. We estimate that the value of the health benefits exceed current average expenditures on PA management for the 1/3 of PAs with the largest local populations, although not for PAs in more remote locations. Our findings highlight how quantifying the contributions to the wellbeing of local populations can support conservation objectives, even if global environmental benefits are not a high priority for decision makers.

Road Infrastructure and Primate Conservation: Introducing the Global Primate Roadkill Database

As road infrastructure networks rapidly expand globally, especially in the tropics, previously continuous habitats are being fragmented, resulting in more frequent wildlife-vehicle collisions (WVC). Primates are widespread throughout many sub-/tropical countries, and as their habitats are fragmented, they are increasingly at risk of WVC. We created the Global Primate Roadkill Database (GPRD), the largest available standardized database of primate roadkill incidents. We obtained data from published papers, un-published and citizen science databases, anecdotal reports, news reports, and social media posts. Here, we describe the collection methods for the GPRD and present the most up-to-date version of the database in full. For each primate roadkill incident, we recorded the species killed, the exact location, and the year and month the roadkill was observed. At the time of publication, the GPRD includes 2862 individual primate roadkill records from 41 countries. As primates range in more than twice as many countries, the absence of data from these countries is not necessarily indicative of a lack of primate vehicular collisions. Given the value of these data for addressing both local and global research questions, we encourage conservationists and citizen scientists to contribute to the GPRD so that, together, we can better understand the impact road infrastructure has on primates and evaluate measures which may help mitigate risk-prone areas or species.

National parks and conservation concessions: a comparison between mammal populations in two types of tropical protected areas in Ucayali, Peru

Peru contains the second largest surface area of the Amazon biome. The Peruvian Amazon is threatened by logging, illegal crops, mining, and agricultural expansion. While a number of national parks exist in the Amazon region, privately managed areas like Conservation Concessions can be an attractive complement to existing parks. We compare medium and large mammal communities in a Conservation Concession in Ucayali with the nearby Parque Nacional Sierra del Divisor National Park and describe species relative abundance and richness of both protected areas. Results suggest that Conservation Concessions can harbour an important diversity of mammal species and could provide connections to larger protected areas. However, they are no substitutes for large protected areas, especially for sensitive and threatened species. Further research is needed to demonstrate their complementarity and improve landscape-level connectivity between conservation models.

Correlates of plant β-diversity in Atlantic Forest patches in the Pernambuco Endemism Centre, Northeastern Brazil

Understanding how vegetation structure and floristic composition vary across landscapes is fundamental to understand ecological patterns and for designing conservation actions. In a patch-landscape approach, we assessed the β-diversity (q0 order – rare species, q1 order – common species, and q2 order – dominant species) of plants between forest patches and surveyed plots in Atlantic Forest patches located in the Pernambuco Endemism Centre, northeastern Brazil. Furthermore, we tested the influence of predictor variables linked to landscape (forest cover and edge density) and habitat (basal area), as well as the geographical distance between forest patches and plots on the β-diversity in each forest patch and plot. We measured and identified a total of 1,682 individuals (trees and lianas), corresponding to 248 species, 116 genera, and 56 families in 10 plots (50 × 2 m) from each forest patch. The β-diversity presented lower values for the Mata de Água Azul patch at a landscape scale (i.e., between forest patches) and Mata dos Macacos patch at a site scale (i.e., between plots) for all orders. Geographical distance positively influenced the β-diversity at the landscape scale, and higher turnover between plots (e.g., within forest patches) was positively associated with differences in geographical distance, edge density, forest cover, and basal area. Our results indicate the need to conserve forest patches distributed across a wide area (distant sites) that encompass different landscape contexts with different vegetation structures, in order to conserve greater floristic diversity.

Messaging Should Reflect the Nuanced Relationship between Land Change and Zoonotic Disease Risk

A hallmark of the media publicity surrounding COVID-19 has been the message that land change causes zoonotic diseases to spill over from wild animals to humans. The secondary peer-reviewed literature sends a similar message. However, as indicated in the primary peer-reviewed literature, the complexity of interacting variables involved in zoonotic disease spillover makes it unlikely for such a claim to be universally applicable. The secondary peer-reviewed literature and the mainstream media also differ markedly from the primary peer-reviewed literature in their lack of nuance in messaging about the relationship between land change and spillover risk. We advocate accurate, nuanced messaging for the sake of the local communities at greatest risk from zoonotic disease, for the sake of scientific credibility, and so that proportionate attention may be given to other possible drivers of spillover risk.

Carbon payments can cost-effectively improve logging sustainability in the Amazon

Selective logging is pervasive across the tropics and unsustainable logging depletes forest biodiversity and carbon stocks. Improving the sustainability of logging will be crucial for meeting climate targets. Carbon-based payment for ecosystem service schemes, including REDD+, give economic value to standing forests and can protect them from degradation, but only if the revenue from carbon payments is greater than the opportunity cost of forgone or reduced logging. We currently lack understanding of whether carbon payments are feasible for protecting Amazonian forests from logging, despite the Amazon holding the largest unexploited timber reserves and an expanding logging sector. Using financial data and inventories of >660,000 trees covering 52,000 ha of Brazilian forest concessions, we estimate the carbon price required to protect forests from logging. We estimate that a carbon price of $7.90 per tCO₂ is sufficient to match the opportunity costs of all logging and fund protection of primary forest. Alternatively, improving the sustainability of logging operations by ensuring a greater proportion of trees are left uncut requires only slightly higher investments of $7.97-10.45 per tCO₂. These prices fall well below the current compliance market rate and demonstrate a cost-effective opportunity to safeguard large tracts of the Amazon rainforest from further degradation.

Hunting pressure is a key contributor to the impending extinction of Bornean wild cattle

Widespread and unregulated hunting of ungulates in Southeast Asia is resulting in population declines and localised extinctions. Increased access to previously remote tropical forest following logging and changes in land-use facilitates hunting of elusive wild cattle in Borneo, which preferentially select secluded habitat. We collated the first population parameters for the Endangered Bornean banteng Bos javanicus lowi and developed population models to simulate the effect of different hunting offtake rates on survival and the recovery of the population using reintroduced captive-bred individuals. Our findings suggest that the banteng population in Sabah is geographically divided into 4 management units based on connectivity: the Northeast, Sipitang (West), Central and Southeast, which all require active management to prevent further population decline and local extinction. With only 1% offtake, population growth ceased in the Northeast and Sipitang. In the Southeast and Central units, growth ceased at 2 and 4% offtake, respectively. Extinction was estimated at 21-39 yr when offtake was 5%, occurring first in Sipitang and last in the Central unit. Supplementing the population with captive-bred individuals suggested that inbreeding was likely to limit population growth if using ≤20 founder individuals. Translocating 2 individuals for a 10 yr period, starting after 20 yr of captive breeding resulted in a faster population recovery over 100 yr and a lower extinction probability. Our results suggest that shielding the population against further losses from hunting will be key to their survival in the wild, provided that active management in the form of captive breeding is developed in the interim.

A camera trap record of Asiatic Golden Cat Catopuma temminckii (Vigors & Horsfield, 1827) (Mammalia: Carnivora: Felidae) in State Land Forest, Merapoh, Pahang, Malaysia

The Asiatic Golden Cat Catopuma temminckii is poorly studied in Peninsular Malaysia.  We deployed 12 camera traps to assess the wildlife diversity in the unprotected State Land Forest of Merapoh, Pahang State.  During the period from August to October 2019, one Asiatic Golden Cat was photographed at a single camera trap station.  This record outside the protected area network emphasizes the importance of wildlife corridors.  This State Land Forest is located between Forest Reserve and Taman Negara National Park.  Therefore, appropriate conservation measures must be taken in order to maintain this site as a wildlife corridor.

Phytoplankton diversity in relation to physicochemical attributes and water quality of Mandakini River, Garhwal Himalaya

Phytoplankton are important biological indicators of water quality. This current study assessed the physicochemical parameters and phytoplankton diversity of Mandakini River, an important tributary of the River Ganga. Water and phytoplankton samples were collected from three sampling sites located at three different altitudes for a period of twelve months (July 2018-June 2019). Water samples were analyzed for fourteen important physicochemical parameters along with the identification of phytoplankton by following the standard methodology. A total of 21 species of phytoplankton under three major groups Bacillariophyceae (Cymbella aequalis, Diatoma vulgaris, Fragilaria arcus, Frustulia rhomboids, Gomphonema geminatum, Navicula confervacea, Nitzchia diversa, and Synedra ulna); Chlorophyceae (Volvox sp., Cladophora glomerata, Closterium longissima, Hydrodictyon sp., Microspora amoena, Spirogyra sp., Oedogonium sp., Ulothrix zonata, and Zygnema cylindrospermum); and Cyanophyceae (Anabaena ambigua, Chlorococcum humicola, Nodularia sp., and Oscillatoria sancta) were observed and recorded during the study period. Site S₃ (Rudraprayag) had the highest species diversity. From this study, the effect of physicochemical parameters on the diversity and density of phytoplankton was observed. It also includes the overall significance of phytoplankton and physicochemical parameters to the water quality of the Mandakini River along with the key factors that were responsible for the degradation of water quality. The current study also provides baseline information to future researchers working in a similar discipline.

Landslides in the Andes: Forests can provide cost-effective landslide regulation services

Landslides cause billions of dollars (USD) in damage and hundreds of life losses every year in mountainous areas globally, and these effects are exacerbated by climate change and increased human occupation of vulnerable areas. In many mountainous regions forests deliver slope stability, helping to prevent landslides. However, forests are progressively converted into other land uses in many mountainous regions. In this study, we focus on the Colombian Andes, the most populated and deadly landslide-prone part of Colombia. We aim to determine the difference in frequency of landslides from forested and non-forested areas, and subsequently, quantify the potential costs and benefits of protecting forest and of restoring forest from agricultural lands. To that end, we combine economic data with geographical information related to public and private infrastructure, land use, and landslide susceptibility. Analyzing the national landslide database of Colombia, we established that landslides are almost six times (581%) more likely to occur on non-forested lands than on forested lands. From an economic perspective, by preventing landslides, forests provide a net benefit through the provision of slope stability services. Our most conservative estimates indicate it is 16 times more cost-effective to promote forest corridors, via conservation or reforestation along roads by paying farmers and cattle herders their opportunity costs, than for the public to pay the expected value of landslide damage. Our analysis provides strong evidence that vegetated hillsides can provide a cost-effective ecosystem service approach to mitigate economic losses due to landslides in one of the world's most landslide prone areas.

A Quantitative Analysis of Surface Changes on an Abandoned Forest Road in the Lejowa Valley (Tatra Mountains, Poland)

The main aim of this research was to determine the magnitude of geomorphologic changes within a section of a forest road. The research was carried out in the Lejowa Valley in the Tatra Mountains. The measurements of the surface of the road were performed using a RIEGL VZ-4000 terrestrial laser scanner (TLS). TLS models for 2017, 2018, and 2019 served as the basis for the determination of quantitative and spatial relief transformations. The net annual change on the studied road within the first period equaled −884 m3 ha−1 year−1, and for the second period −370 m3 ha−1 year−1. Changes across the accumulation fan ranged from −265 m3 ha−1 year−1 to +36 m3 ha−1 year−1. The average rate of erosion on the studied abandoned road is similar, and sometimes even greater than that on roads which are still in use. Our research shows that improper road location may lead to irreversible changes to the natural environment. The planning of a forest road must take into account natural conditions, otherwise progressive relief transformations may lead to significant surface changes and the road may be excluded from use.

Effects of tropical forest conversion on soil and aquatic systems in southwestern Brazilian Amazonia: A synthesis

Southwestern Brazilian Amazonia has suffered intense forest conversion in a short period of time (~60 years) and deforestation is ongoing. Around 70% of the deforested area has been designated for cattle ranching. This forest clearing and pasture establishment is abruptly disrupting the functioning of the ecosystem. In this paper, we provide an overview of the effects of land conversion from forest to pasture on the soil and aquatic systems. Forest conversion to pasture has two clear effects: a) an on-site effect on the hillslope domain and 2) an off-site effect on the river system. The conversion of forest to pasture affects the soil physical-chemical properties, soil carbon content, water resources, and aquatic system. However, many of these changes are not straightforward or obvious. For example, in some conditions, the soil carbon stock increases in pasture. Despite the advances in our understanding of the effects of land conversion on environmental processes, knowledge gaps persist, and we identify some research needs.

Habitat degradation and indiscriminate hunting differentially impact faunal communities in the Southeast Asian tropical biodiversity hotspot

Habitat degradation and hunting have caused the widespread loss of larger vertebrate species (defaunation) from tropical biodiversity hotspots. However, these defaunation drivers impact vertebrate biodiversity in different ways and, therefore, require different conservation interventions. We conducted landscape-scale camera-trap surveys across six study sites in Southeast Asia to assess how moderate degradation and intensive, indiscriminate hunting differentially impact tropical terrestrial mammals and birds. We found that functional extinction rates were higher in hunted compared to degraded sites. Species found in both sites had lower occupancies in the hunted sites. Canopy closure was the main predictor of occurrence in the degraded sites, while village density primarily influenced occurrence in the hunted sites. Our findings suggest that intensive, indiscriminate hunting may be a more immediate threat than moderate habitat degradation for tropical faunal communities, and that conservation stakeholders should focus as much on overhunting as on habitat conservation to address the defaunation crisis.

Counting Sunda clouded leopards with confidence: incorporating individual heterogeneity in density estimates

Even with intensive sampling effort, data often remain sparse when estimating population density of elusive species such as the Sunda clouded leopard Neofelis diardi. An inadequate number of recaptures can make it difficult to account for heterogeneity in detection parameters. We used data from large-scale camera-trapping surveys in three forest reserves in Sabah, Malaysian Borneo, to (1) examine whether a high-density camera-trap network increases the number of recaptures for females, which tend to be more difficult to detect, thus improving the accuracy of density estimates; (2) compare density estimates from models incorporating individual heterogeneity in detection parameters with estimates from the null model to evaluate its potential bias; and (3) investigate how the size of the camera-trap grid affects density and movement estimates. We found that individual heterogeneity could not be incorporated in the single-site data analysis and only conservative null model estimates could be generated. However, aggregating data across study sites enabled us to account for individual heterogeneity and we estimated densities of 1.27–2.82 individuals/100 km2, 2–3 times higher than estimates from null models. In light of these findings, it is possible that earlier studies underestimated population density. Similar densities found in well-managed forest and recently selectively logged forest suggest that Sunda clouded leopards are relatively resilient to forest disturbances. Our analysis also revealed that camera-trapping grids for Sunda clouded leopard density estimations should cover large areas (c. 250 km2), although smaller grids could be appropriate if density or detectability are higher.

Low-intensity logging and hunting have long-term effects on seed dispersal but not fecundity in Afrotropical forests

Hunting and logging, ubiquitous human disturbances in tropical forests, have the potential to alter the ecological processes that govern population recruitment and community composition. Hunting-induced declines in populations of seed-dispersing animals are expected to reduce dispersal of the tree species that rely on them, resulting in potentially greater distance- and density-dependent mortality. At the same time, selective logging may alter competitive interactions among tree species, releasing remaining trees from light, nutrient or space limitations. Taken together, these disturbances may alter the community composition of tropical forests, with implications for carbon storage, biodiversity conservation and ecosystem function. To evaluate the effects of hunting and logging on tree fecundity and seed dispersal, we use 3 years of seed rain data from a large-scale observational experiment in previously logged, hunted and protected forests in northern Republic of Congo (Brazzaville). We find that low-intensity logging had a meaningful long-term effect on species-specific seed dispersal distances, though the direction and magnitude varied and was not congruent within dispersal vector. Tree fecundity increased with tree diameter, but did not differ appreciably across disturbance regimes. The species-specific dispersal responses to logging in this study point towards the long-lasting toll of disturbance on ecological function and highlight the necessity of conserving intact forest.

Reconciling certification and intact forest landscape conservation

In 2014, the Forest Stewardship Council (FSC) added a new criterion to its principles that requires protection of intact forest landscapes (IFLs). An IFL is an extensive area of forest that lacks roads and other signs of human activity as detected through remote sensing. In the Congo basin, our analysis of road networks in formally approved concessionary logging areas revealed greater loss of IFL in certified than in noncertified concessions. In areas of informal (i.e., nonregulated) extraction, road networks are known to be less detectable by remote sensing. Under the current definition of IFL, companies certified under FSC standards are likely to be penalized relative to the noncertified as well as the informal logging sector on account of their planned road networks, despite an otherwise better standard of forest management. This could ultimately undermine certification and its wider adoption, with implications for the future of sustainable forest management.