This Doctoral Dissertation Enhancement award provides funding for a final trip to India for coPI Mandle to carry out a suite of additional field measurements for her dissertation research. The focus of the study is the interactive effects of harvest, grazing, and fire on the population dynamics of a harvested palm in a prime biodiversity site in India?s Western Ghats, where human activities strongly impact native plant communities.

Although a number of studies of demographic effects of palm leaf-harvest have been done previously, this study breaks new intellectual ground through the application of new statistical population modeling techniques. The combination of multi-site comparative studies with explicit experimental studies will strengthen the coPI?s thesis.

Research focused at the nexus between native plant populations and human activities is especially valuable in tropical sites such as the Western Ghats. What is learned in this project could potentially be both practically-applicable locally and a model approach for such research at many types of sites, particularly in the tropics.

The broader impacts of this project are strong with respect to the level of cross-interaction between countries, the incorporation of Indian colleagues and local people in the field, as well as its potential to develop new modeling and experimental approaches for plant conservation efforts in the face of significant on-going human activities. This enhancement provides additional funding for international research to a current NSF Graduate Research Fellowship awardee.

Project Report

This international Doctoral Dissertation Enhancement project investigated the interactive effects of widespread, concurrent management activities on ecological processes and biodiversity in India’s Western Ghats biodiversity hotspot, where human activities strongly impact the natural environment. Determining the compatibility between different forms of human land management and the conservation of biodiversity is necessary to maintain biodiversity while meeting human needs both in the present and over the long term. Results of this project increased understanding of the ways in which human activities affect the natural environment, contributing to management of these important ecosystems in India while also providing a model for understanding and conservation in human-managed tropical systems more broadly. This project also supported the professional training of one U.S.-based graduate student and collaboration with researchers from two environmental research non-governmental organizations (NGOs) in India. Further details about these outcomes are provided below. Human activities are having an unprecedented impact on ecological processes and biodiversity around the globe, with cascading consequences for our own well-being. The majority of the world's remaining terrestrial biodiversity occurs in human-modified tropical ecosystems. Human activities commonly have multiple concurrent effects on ecosystems. For example, within our study system and throughout much of the tropics, people use fire in order to manage landscapes for livestock grazing and wild plant harvest. Although these activities (fire, grazing and harvest) routinely occur together, ecological studies have focused predominately on their isolated, individual effects. It is often assumed – though rarely tested – that the combined effects of these and other human activities are either additive (equal to the sum of individual effects) or that there are synergistic interactions such that the combined effects have even greater negative ecological consequences than the sum of individual effects. This project explicitly tested for interactive effects among fire, grazing and harvest to understand how these activities combine to affect mountain date palm (Phoenix loureiroi) individuals and populations. We found that interactive effects were common. This indicates that studying these land management activities individually will not lead to realistic conclusions about their combined effects. Importantly, we found that a number of interactive effects were sub-additive rather than synergistic. This suggests that the combined effects of land management activities may not always be as drastic as would be predicted from studying each activity individually. This project focused on seasonally dry tropical savanna woodlands, which at a global level are heavily impacted by human activities but understudied compared to tropical moist forests. We found that the moderate intensity forms of management that we studied (fire, livestock grazing and wild plant harvest) had little effect on overall levels of species or functional diversity of the savanna woodlands in the Western Ghats region of India. However, we also found that areas with higher intensities of human activities had more common, widespread species and fewer of the rare, narrowly distributed species that are often of particular conservation concern. This contributes to evidence the human activities contribute to increasing similarity in species composition among formerly distinct areas. Our findings suggest that human-managed savanna woodlands can maintain comparable levels of diversity to those protected from human use and contribute to conservation of native plant diversity in the Western Ghats. However, the changes in the kinds of species present also indicates that human-managed savanna woodlands can complement but not substitute for protected areas in meeting conservation objectives. Overall, our findings contribute to understanding the ecological effects of human activities and highlight the necessity of determining interactions among drivers of ecological processes in order to effectively manage the consequences of environmental change in India and beyond. Our results were shared with the international scientific community through peer-reviewed publication in scientific journals and presentations at international conferences. Locally, this project is contributing to environmental management decisions being made in South India. Results were shared and discussed with the local communities who manage and depend on the focal ecosystems. The two collaborating Indian NGOs are continuing to integrate this information into their work with indigenous communities to obtain management rights and develop plans for sustainable management, as provided under recent national legislation in India. Beyond contributing to management and conservation of these important systems, this project has had a number of additional broader impacts. This project contributed to the training of one U.S.-based graduate student, leading to successful completion of the student’s doctoral dissertation and continuation in the field of applied ecology and conservation science as a post-doctoral researcher. The project also strengthened international research networks, fostering collaboration with scientists from two Indian environmental NGOs in the design, data collection, analysis and dissemination of research results. Collaboration continues beyond the completion of this project.

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