Climate-driven environmental changes influence the spatial spread, persistence, and community dynamics of plant populations. Ecological theory has focused on determining which populations will persist and spread in response to these changes and how they will do so. I build on this theory by investigating how climate change affects the mechanisms that influence the spread of invasions, how structured plant populations keep pace with climate change, and if communities of native plants can recover after a biological invasion in the face of climate change. First, I develop a spatial population model to investigate how climate change affects the spread of ecosystem engineers, which are organisms that change the availability of resources in their environment. I apply this model to salt marsh grasses, which engineer their environment by increasing marsh elevation via sediment accumulation. I find that climate-driven sea-level rise reverses the conditions that promote the spread of these ecosystem engineers. Next, I develop a spatial model of a stage-structured plant population, which shifts in response to climate change. I use this model to determine if older trees left behind when the habitat shifts play any ecological role in the population. I find that these zombie forests are critical to the persistence of the population, dispersing seeds into the core population as it moves. Finally, I investigate how a series of extreme climate events, including drought, fire, and extreme precipitation, affect the ability of native plant communities to recover after removal of an invasive species. Analyzing seven years of field data, I find that the recovery of native plant communities after invader removal is resilient to major climate perturbations. Together, these studies identify conditions and mechanisms that limit the spread of plant invasions and promote the persistence of vulnerable plant populations in the face of climate change.

This book focuses on how climate affects or affected the biosphere and vice versa both in the present and in the past. The chapters describe how ecosystems from the Antarctic and Arctic, and from other latitudes, respond to global climate change. The papers highlight plant responses to atmospheric CO2 increase, to global warming and to increased ultraviolet-B radiation as a result of stratospheric ozone depletion.

This open access book describes the serious threat of invasive species to native ecosystems. Invasive species have caused and will continue to cause enormous ecological and economic damage with ever increasing world trade. This multi-disciplinary book, written by over 100 national experts, presents the latest research on a wide range of natural science and social science fields that explore the ecology, impacts, and practical tools for management of invasive species. It covers species of all taxonomic groups from insects and pathogens, to plants, vertebrates, and aquatic organisms that impact a diversity of habitats in forests, rangelands and grasslands of the United States. It is well-illustrated, provides summaries of the most important invasive species and issues impacting all regions of the country, and includes a comprehensive primary reference list for each topic. This scientific synthesis provides the cultural, economic, scientific and social context for addressing environmental challenges posed by invasive species and will be a valuable resource for scholars, policy makers, natural resource managers and practitioners.

Understanding the relative importance of density-dependent and density-independent factors in driving population dynamics is one of the oldest challenges in ecology, and may play a critical role in predicting the effects of climate change on populations. We used long-term observational data to describe patterns in plant population regulation for 57 forb and grass species from three different ecosystems (arid desert grassland, semiarid sagebrush steppe, and subhumid mixed-grass prairie). Using a hierarchical partitioning approach, we (i) quantified the relative influence of conspecific density, heterospecific composition, and climate on temporal variation in population growth rates, and (ii) asked how the relative importance of these drivers depends on site aridity, species growth form and life expectancy, and abundance and spatial patterns. The data from one of the sites in this analysis are presented in one of the chapters of this thesis. We found that density-dependence had the strongest effect on species. Climate often had a significant effect, but its strength depended on growth form. Community composition rarely explained significant variation in growth rates. The relative importance of density, composition, and climate did not vary among sites, but was related to species' life histories: compared to forbs, grasses were more sensitive to climate drivers. Abundance and spatial clustering were negatively correlated with the importance of density dependence, suggesting that local rarity is a consequence of self-limitation. Our results show that interspecific interactions play a weaker role than intraspecific interactions and climate variability in regulating plant populations. Forecasting the impacts of climate change on populations may require understanding how changes in climate variables will affect the strength of density-dependence, especially for rare species.

This report discusses the relationship between population and environmental change, the forces that mediate this relationship, and how population dynamics specifically affect climate change and land-use change.

Population and Climate Change provides the first systematic in-depth treatment of links between two major themes of the 21st century: population growth (and associated demographic trends such as aging) and climate change. It is written by a multidisciplinary team of authors from the International Institute for Applied Systems Analysis who integrate both natural science and social science perspectives in a way that is comprehensible to members of both communities. The book will be of primary interest to researchers in the fields of climate change, demography, and economics. It will also be useful to policy-makers and NGOs dealing with issues of population dynamics and climate change, and to teachers and students in courses such as environmental studies, demography, climatology, economics, earth systems science, and international relations.