Movement is a fundamental property of nearly all life on earth. The need to move is driven by a variety of requirements, including escape from harsh weather, establishment of populations in new places, and procurement of food and mates. Understanding and predicting the extent of movement is critical for knowing why and how organisms occur where they do. It is also essential for forecasting impacts of habitat alteration and climate change on biodiversity. But movement is difficult to measure, even for one species of plant or animal and particularly at the large areas over which organisms regularly move and biodiversity conservation occurs. This study uses novel techniques to do what has so far been nearly impossible - to measure movement over long distances for a diverse group of plant and animal species. First, it uses a novel technique, 'tagging' entire communities with enriched nitrogen, which can be used to track the movement of any organism in the community exposed to that source nitrogen. Second, dispersal will be quantified in a unique, large-scale, well-replicated, landscape experiment - one that is unprecedented in its size and longevity for testing effects of corridors, thin strips of habitat that connect otherwise isolated habitat patches. The investigators will measure dispersal for 50 species of plants and animals across landscapes that vary in connectivity.
This study is important for effective conservation because it will measure the extent to which habitat fragmentation reduces the ability of plant and animal species to move through a landscape, and the extent to which wildlife corridors help organisms move across fragmented landscapes. Corridors are considered to be one of the most important tools available to help solve the many problems caused by habitat loss and fragmentation. Corridors may provide superhighways for plants and animals, and are expected to see increased traffic as climate changes, allowing organisms to shift their ranges as needed. This project will train undergraduate students through research and through the continuation of an award-winning collaborative program focused on mentoring an especially diverse set of students; support a K-12 program that provides environmental education to underprivileged youth; maintain scientific infrastructure (the world's largest experiment on habitat corridors); and provide a long-term database on how organisms respond to corridors.
Loss of habitat – including forests and grasslands – is the single greatest cause of loss of biodiversity. Importantly, in the context of this project, habitat loss is coupled with another element that is also detrimental to biodiversity, which is the reduced size and increased separation of the remaining habitat. This process is termed habitat fragmentation. A great scientific challenge that bears directly on this process is how to restore landscapes where habitat has been lost and fragmented. This project is aimed directly at this challenge. We tested the most popular strategy to protect biodiversity in such landscapes, which is to create habitat corridors (strips of habitat that connect otherwise isolated patches of the same habitat). These corridors are intended as superhighways for plants and animals, increasing their movement across fragmented landscapes. Project personnel tested the effects of corridors by creating patches of pine savannah habitat, some of the patches were connected by corridors and others were not. These experimental landscapes, which have now been in existence for twenty years, are of large size and replicated, allowing direct tests of the role of corridors in increasing plant and animal movement. Above and beyond the experiment, this specific project employed a novel technique to track movement. We used a non-toxic, stable, and rare isotope of nitrogen to chemically mark a large number of plants, as well as a large number of animals that eat the plants, in the center of some patches. We could then recover marked seeds and insects at various distances from where we had sprayed the nitrogen marker through intensive collection efforts. The animals dispersed on their own, and the plants dispersed by seeds that were carried by wind or inside animals after being swallowed and later defecated. Our novel technique allowed us to solve a great challenge in dispersal studies: the rare, long distance dispersal events largely determine the rate at which populations and communities of plants and animals move across a landscape, but tracking long distance dispersal is inherently difficult, as it is rare. It is a needle in a haystack problem. With our chemical marking technique, we were able to collect thousands of seeds and insects, and separate the needle (the one or a few insects or seeds in a sample that had travelled the long distance from our marked patch) from the haystack (potentially hundreds or thousands of insects or seeds that came from other locations ) . By analyzing the collected samples for the marker, we were able to construct dispersal kernels (graphs showing the probability of dispersing increasingly far distances) for plants and animals in fragmented habitats, with and without corridors. To provide a control, we used the same marking and sampling techniques on the same set of plants and animals in unfragmented landscapes. Although we are still in the process of analyzing our samples and constructing the dispersal kernels, we can tentatively conclude that corridors indeed facilitated movement of plants and animals across fragmented landscapes and that many species dispersed surprisingly long distances, especially in unfragmented landscapes. These results have direct implications for predicting the ability of plants and animals to respond to habitat loss and fragmentation, and for the potential success of conservation measures such as the creation of landscape corridors. We were able to show that a large fraction of plants and animals can disperse long distances, and benefit from the creation of superhighways in the form of landscape corridors. One particularly novel finding during this study period is the role habitat fragmentation and corridors play in the movement of seeds dispersed by wind. Wind dynamics are affected by habitat fragmentation, and corridors help to guide wind and the plants dispersed by it. Our results are also applicable for understanding how corridors can facilitate a broad range of ecosystem services provided by animals as they move across landscapes. Examples include pollination by insects and seed dispersal by birds. Our work has also shown how corridors have positive effects on ecology and conservation in fragmented landscapes, as has been theorized, and that corridors have few, almost negligible, negative effects (that is, they do not spread invasives, disturbances, or predators or parasites in ways that are harmful to target species). Finally, this project provided opportunities for approximately 25 undergraduate and graduate students to gain experience in field ecology; many were from underrepresented groups and all were mentored by senior personnel.
