Sophie Jane Tudge

Few studies explicitly assess the robustness and practicality of occupancy analysis informed by local inhabitants, compared to estimates from conventional monitoring methods within different contexts. This study evaluates the efficacy and robustness of occupancy models based on camera trap data, and two locally informed methods: seasonal interviews and hunter diaries, for monitoring 13 hunted mammal species in south-eastern Cameroon. We triangulate estimates of detectability and occupancy to assess the precision and comparability of their estimates for different species, and their cost. Camera trap estimates are comparable with estimates from locally informed methods in 7 of 11 available cases, but produced the lowest detection probabilities for all species in both villages. While camera traps provide robust estimates for abundant species with a high detection probability, locally informed methods can provide estimates of occupancy comparable to camera trap estimates, but at significantly less cost. They are particularly useful where camera trap detection rates (p) are too low to produce robust occupancy model estimates, notably for rare or cryptic species. The methods, survey effort and animals that can be monitored robustly vary between villages. As such, consideration should be given before monitoring commences to ensure that the most effective and informative approach is used.

Human activity in African tropical rainforests continues to threaten wild mammals. Many rural communities are dependent on hunting, yet there is a widespread lack of baseline data on ecology and the sustainability of hunting. We investigated the impacts of human activity on mammal species composition and distributions within a community forest surrounding a village in the buffer zone of the Dja Biosphere Reserve in south-east Cameroon. We conducted a camera-trap survey in August–November 2017 and detected 24 mammal species, including Critically Endangered western lowland gorilla Gorilla gorilla gorilla, Endangered central African chimpanzee Pan troglodytes troglodytes and Endangered tree pangolin Phataginus tricuspis. We used occupancy analysis to explore relationships between indicators of human activity (distance to a road and the Reserve), habitat quality (distance to the river and tree cover) and the distributions of species. We found that the local distribution of threatened mammals was not apparently limited by human activity, and proximity to the road did not negatively influence occupancy for any species. However, most of the Reserve's large species were not detected, including the African forest elephant Loxodonta cyclotis and the largest ungulates, and the occupancy of two species commonly hunted for wild meat was positively correlated with distance from the village, indicating hunting may be unsustainable. Our results show that the community forest provides habitat for threatened species outside the Reserve and in close proximity to people. However, effective conservation management will require continued monitoring and research to determine whether current rates of hunting are sustainable.

Concerns about the impacts of climate change have led to increased targets for biofuel in the global energy market. First-generation biofuel crops contain oil, sugar or starch and are usually also grown for food, whereas second-generation biofuel is derived from non-food sources, including lignocellulosic crops, fast-growing trees, crop residues and waste. Biofuel production drives land-use change, a major cause of biodiversity loss, but there is limited knowledge of how different biofuel crops affect local biodiversity. Therefore, a more detailed understanding could inform more environmentally-conscious decisions about where to grow which biofuel crops. We synthesised data from 116 sources where a potential biofuel crop was grown and estimated how two measures of local biodiversity, species richness and total abundance, responded to different crops. Local species richness and abundance were 37% and 49% lower at sites planted with first-generation biofuel crops than in sites with primary vegetation. Soybean, wheat, maize and oil palm had the worst effects; the worst affected regions were Asia and Central and South America; and plant species richness and vertebrate abundance were the worst affected biodiversity measures. Second-generation biofuels had smaller, but still significant, effects: species richness and abundance were 19% and 25%, respectively, lower in such sites than in primary vegetation. Our models suggest that land clearance to cultivate biofuel crops reduces local biodiversity. However, the yield of biofuel from different crops influences the biodiversity impacts per unit of energy generated, and the geographic and taxonomic variation in effects are also relevant for making sustainable land-use decisions.

Tree plantations are expanding globally to satisfy demands for wood, food, energy, oil and other ecosystem services, often replacing primary vegetation. Plantations are generally less biodiverse than primary vegetation, yet the effects of plantation age on biodiversity are not well understood. More accurate estimations of biodiversity within plantations over time could improve predictions of the ecological effects of tree planting, guiding more sustainable land use and management decisions. Here, we assess the effects of plantation age on the abundance and number of species of invertebrates, birds, plants, mammals, amphibians, reptiles and lichens, and on compositional similarity to minimally-used primary vegetation. We find that plantations usually support fewer species than both minimally-used primary vegetation and mature secondary vegetation, fewer individuals, and some novel species (i.e. species not also found in primary vegetation). We also find that, on a global scale, plantation age has positive effects on species richness, the abundance of individuals, and compositional similarity to primary vegetation. However, geographic realm, biome, management intensity and plantation type influence the biodiversity trends. We also include a case study for oil palm, showing that species richness increases with oil palm plantation age. Nevertheless, plantations typically remain less biodiverse than natural vegetation even thirty years after planting, especially in the tropics, where compositional similarity between plantations and minimally-used primary vegetation remains approximately 20% lower than the non-tropics. Our results highlight the negative ecological consequences of establishing new plantations in place of primary vegetation or restoration, yet we also reveal spatio-temporal differences in plantation biodiversity.

1. To combat climate change, bioenergy is expected to play a more substantial role in the global energy mix, necessitating the expansion of energy crop plantations during the 21st century. Low-quality or abandoned agricultural land is commonly proposed for growing energy crops. However, restoring such agricultural land back to natural vegetation is also key for global biodiversity conservation and carbon sequestration. Thus, understanding the ecological implications of land-use changes involving both energy crop plantations and restoration is required.

2. Here, we use biodiversity data to calculate the Biodiversity Intactness Index (BII) in different land uses, including energy crop plantations. We combine our BII models with maps of land use, crop yields and priority areas for restoration to estimate the effects on BII of changes in land use, from the current day, due to bioenergy expansion. We then compare the effects on BII of replacing either any land with energy crops, or only existing agricultural land that is a priority for restoration. Finally, we contrast the effects on BII of planting energy crops versus restoring natural vegetation in priority areas for restoration.

3. Planting energy crops in places with relatively high amounts of natural vegetation and high BII would substantially reduce BII.

4. Planting energy crops only on existing agricultural land that is a priority for restoration would result in less negative effects on BII than planting such crops in high BII areas, and small increases in BII in places with less remaining natural vegetation. However, restoring natural vegetation in priority areas, rather than expanding energy crops, would result in better outcomes for BII.

5. Contrasting the spatial effects on BII of planting energy crops compared with restoring natural vegetation highlights places where energy crops could be the least detrimental to BII, such as Central Europe and the east coasts of the USA and China.

6. Synthesis and applications. While restoration is the best strategy for biodiversity, planting energy crops on agricultural land rather than replacing natural vegetation could minimise losses in biodiversity intactness. However, achieving targets for bioenergy, climate change and restoration will require strategic land-use planning to minimise ecological compromises.