Doctor of Philosophy in Forestry (PhD)
Ecosystem services recovery in an era of novel forest disturbances
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Forest restoration in tropical systems
Agriculture is the most extensive global land use and a leading cause of biodiversity loss. Organic farming is often promoted as a means of reducing agricultural impacts on biodiversity by reducing or avoiding chemical fertilizers and pesticides, and can result in a 30 percent increase in biodiversity for some species in some systems. A potential trade-off is that organic agriculture can lower crop yields, thereby requiring a greater land area to meet crop production goals. In this study, I examined whether forest cover surrounding rice wetlands can reduce the trade-off between biodiversity and productivity via comparison of paired organic and conventional farms. I compared abundance, Simpson diversity, and rarefied richness of amphibians, and abundance of arthropods in organic and conventional rice wetlands in four districts in Kerala, southern India, from July to October of 2016. I selected 31 organic rice fields and paired each with a nearby conventional field. Pairs were located to maximize the variation in forest cover in the landscape surrounding the fields. Farmers provided data on mean rice yields of each farm.Amphibians were significantly more abundant and diverse in organic fields, and species composition differed from those of conventional fields. Arthropods were more abundant in organic fields. While mean yield (tons of rice/hectare) of organic farms was significantly lower than in conventional farms, landscape context ameliorated the trade-off between productivity and biodiversity. In organic fields surrounded by more forest patches, rice yields did not decrease as much compared to the landscapes with less forest, while the increase in biodiversity (as compared to nearby conventional agriculture) was not as large. My results suggest that forested landscapes reduce the trade-off between biodiversity and productivity in rice fields in Kerala. These results could aid in designing agricultural ecosystems that maximize biodiversity benefits. For example, promoting more diversified tree-based agroecosystems, and protecting remaining uncultivated areas in the landscape could improve farmland biodiversity while minimizing the impacts to the agricultural productivity of the landscape. Furthermore, in intensively managed landscapes comprised of cropland and urban land cover, organic farming may have a larger effect on biodiversity than in landscapes with more forest cover.
Rural small-holder farmers in the tropics rely on forests for multiple ecosystem services, such as provisioning services for fuelwood, timber, wild foods and medicinal plants. Yet many of these forests are undergoing degradation and loss, thus jeopardizing long-term ecosystem functioning and services. Measuring levels of forest dependence in agricultural communities is key to understanding livelihood sustainability and potential approaches to forest-based poverty alleviation. Understanding the ecological changes in forests where communities collect forest products, particularly fuelwood, is important for identifying approaches to forest conservation. To address these issues, I conducted social and ecological research in southern Malawi. I conducted household surveys (n=157) in agricultural communities to assess levels of forest dependence. I developed a new index to measure forest dependence that incorporates: the diversity of forest products collected to meet household needs, the effort involved in collection, relative wealth, and alternative livelihood strategies. I compared the index values for the study area to relative forest income values, the proportion of total income comprised by forest-derived income, which is the commonly used measurement of forest dependence. I showed that the relative forest income approach may underestimate levels of forest dependence, and that my new index provides insights into additional livelihood aspects of household forest dependence. I investigated tree species richness, abundance, diversity, composition and aboveground carbon (AGC) in forest plots (n=86) in the miombo woodlands where the farming communities harvest fuelwood, and compared them to reference sites in relatively undisturbed forests. I investigated whether proxies for harvesting access (elevation and distance to the main road) and harvesting pressure (number of settlements within a 3 km buffer) were correlated with the vegetation characteristics in the fuelwood harvesting sites. Tree species richness, abundance, diversity and AGC were lower in fuelwood harvesting sites than reference sites, species composition was significantly different, and the proxies for harvesting pressure and access were correlated with species abundance and AGC. The findings suggest that long-term sustainability of forest collection may be hindered due to forest degradation, which is problematic given the high forest dependence in the area. Interventions to increase sustainability of the social-ecological system could be explored.