Incorporating Connectivity Into Habitat Assessment And Conservation

How to effectively protect biodiversity against global environmental changes is one of today’s grand challenges,while the concept of resilient habitat network provides leverage to tackle such challenge.As such,it is of great importance to quantify and evaluate the structure and function of habitat network,and a better understanding of its effect on biodiversity is urgently needed as well.Focusing on habitat network under environmental changes,this dissertation proposed a new method to characterize connectivity pattern in dynamic landscapes,demonstrated the importance of such dynamics to biodiversity,and further predicted the potential impacts of environmental changes on habitat network.Here I outline each chapter’s contents and the main findings.In Chapter 1,I gave a brief introduction to the research background and significance.I also took thorough literature reviews to synthesize widely-held generalizations and key findings from previous studies relating to habitat fragmentation and/or connectivity,both theoretical and empirical.Chapter 2 described some fundamental knowledge and basic analytical skills that would be required in the remainder of this dissertation.Chapter 3 proposed a framework that combined land use simulation with functional connectivity assessment.Taking the Three Gorges Reservoir Area as a case study,I tested the robustness of two commonly used functional connectivity models –least-cost modeling and circuit theory – under different cost map parameterizations.The test was conducted at both landscape(i.e.functional connectivity assessment)and local levels(i.e.,habitat prioritization).Results showed that,connectivity assessment and habitat prioritization based on circuit theory had higher robustness and consistency than those based on least-cost modeling.As far as the land use change,it was predicted that forest cover would consistently increase during the year of 2000 and 2030 in the study area,and the same held for functional connectivity.Nevertheless,some key stepping-stone habitat patches were predicted to be encroached by urban expansion,and corridor redundancy was also low for short dispersers in the urban periphery.Thus,more effective protection for stepping-stones and building more corridors in the urban periphery is highly recommended.Chapter 4 presented a novel connectivity model that incorporates both spatial and temporal interactions between habitat patches.The spatio-temporal connectivity model was then applied to three highly dynamic landscapes in the Atlantic Forest,Brazil.When habitat net loss occurred in the landscape,spatio-temporal connectivity could significantly strengthen connectivity pattern.Most importantly,I found that the importance of stepping-stone effect was largely underestimated by previous landscape connectivity models,and it was stepping-stone effect the very dominant in connectivity pattern.Further,I proposed a new hypothesis that posited biodiversity pattern in the community is determined by patch size and landscape history.Using field sampling bird diversity data,I found that species richness of forest specialists could be best explained by patch size and spatio-temporal fluxes from the surrounding landscape into the patch than any other landscape predictors.This result therefore provided strong support for my hypothesis.I further extended the spatio-temporal connectivity model in Chapter 5.I proposed a framework that combined spatio-temporal connectivity model and species distribution models,which was then applied to predict the impact of climate change on species’ range and reachable habitat amount in their habitat network.I chose three typical terrestrial mammals in the North America as my study species: white-tailed deer,Canada lynxes and gray wolves.Results showed that,due to reductions in snowfalls,Canada lynxes were predicted to suffer remarkable range contraction.The other two species were likely to shift northwards with more newly suitable habitat gained.In the context of climate change,the importance of spatio-temporal to species persistence would depend on how climate changes habitat quantity,quality and its spatial configuration,as well as species dispersal ability.Spatio-temporal connectivity is more important to species experiencing range contractions,as it would alleviate the loss of reachable habitat amount for those species.