The low-elevation chaparral shrublands of southern California have long been occupied and modified by humans, but the magnitude and extent of human impact has dramatically increased since the early 1900s. As population growth started to boom in the 1940s, the primary form of habitat conversion transitioned from agriculture to urban and residential development. Now, urban growth is the primary contributor, directly and indirectly, to loss and fragmentation of chaparral landscapes. Different patterns and arrangements of housing development confer different ecological impacts. We found wide variation in the changing extent and pattern of development across the seven counties in the region. Substantial growth in lower-density exurban development has been associated with high frequency of human-caused ignitions as well as the expansion of highly flammable non-native annual grasses. Combined, increases in fire ignitions and the extent of grassland can lead to a positive feedback cycle in which grass promotes fire and shortens the fire-return interval, ultimately extirpating shrub species that are not adapted to short fire intervals. An overlay of a 1930s vegetation map with maps of contemporary vegetation showed a consistent trend of chaparral decline and conversion to sage scrub or grassland. In addition, those areas type-converted to grassland had the highest fire frequency over the latter part of the twentieth century. Thus, a continuing trend of population growth and urban expansion may continue to threaten the extent and intactness of remaining shrubland dominated landscapes. Interactions among housing development, fire ignitions, non-native grasses, roads, and vehicle emissions make fire prevention a complex endeavor. However, land use planning that targets the root cause of conversion, exurban sprawl, could address all of these threats simultaneously.
*Note: This publication comes from a book chapter from Biology and Conservation of Martens, Sables, and Fishers: A New Synthesis (1st edition).
Conservation and management of Martes populations are increasingly informed by quantitative models that predict habitat suitability and population viability. Recent modeling efforts to support fisher (Martes pennanti) reintroduction plan- ning in the state of Washington (USA) and conservation of an isolated fisher population in the southern Sierra Nevada (California, USA) have integrated re- sults from empirical static habitat models, such as resource-selection functions, with those from dynamic population-viability and vegetation models. Additional methods have been developed to identify habitat linkages with potential impor- tance for maintaining interpopulation dispersal. While such modeling frame- works can be useful in integrating data on species distribution, demography, and vegetation response to disturbance, the associated increased data requirements may also increase uncertainty regarding model projections to different places or times. The costs associated with reintroductions generally justify the use of such models to inform the planning process before substantial resources are commit- ted. Given the challenges posed by increasing human demands on forest ecosys- tems, well-constructed quantitative models can be key tools for enhancing the success of wildlife conservation efforts, as long as model uncertainty is consid- ered explicitly, and model results are used for informing decisions rather than predicting outcomes.
Anthropogenic drivers of global change include rising atmospheric concentrations of carbon dioxide and other greenhouse gasses and resulting changes in the climate, as well as nitrogen deposition, biotic invasions, altered disturbance regimes, and land-use change. Predicting the effects of global change on terrestrial plant communities is crucial because of the ecosystem services vegetation provides, from climate regulation to forest products. In this paper, we present a framework for detecting vegetation changes and attributing them to global change drivers that incorporates multiple lines of evidence from spatially extensive monitoring networks, distributed experiments, remotely sensed data, and historical records. Based on a literature review, we summarize observed changes and then describe modeling tools that can forecast the impacts of multiple drivers on plant communities in an era of rapid change. Observed responses to changes in temperature, water, nutrients, land use, and disturbance show strong sensitivity of ecosystem productivity and plant population dynamics to water balance and long-lasting effects of disturbance on plant community dynamics. Persistent effects of land-use change and human-altered fire regimes on vegetation can overshadow or interact with climate change impacts. Models forecasting plant community responses to global change incorporate shifting ecological niches, population dynamics, species interactions, spatially explicit disturbance, ecosystem processes, and plant functional responses. Monitoring, experiments, and models evaluating multiple change drivers are needed to detect and predict vegetation changes in response to 21st century global change.
Fuzzy logic modeling is a useful method for evaluating landscapes for conservation and resource planning and has been successfully used in different types of ecological and environmental studies. A variety of software packages have been produced to facilitate fuzzy logic modeling, but each is either associated with a specific computer program or does not comprise a complete modeling system. The Environmental Evaluation Modeling System (EEMS) is a platform-independent fuzzy logic modeling framework for environmental decision support. EEMS has been designed so that it can easily be adapted to work with different file types and interface with other software systems. It has been implemented to work with NetCDF and CSV file formats as a command line application, in the ArcGIS ModelBuilder environment, and as part of a web-based data exploration tool. In a performance test, EEMS was run using a dataset with four million reporting units per map layer and yielded execution times of less than 30 s.Results from an EEMS model for Utah and the Colorado Plateau show a complex pattern of site sensitivity.
This article examines trends in farming and livelihood activities among forest-dwelling Adivasi farmers (Soligas) in a tiger reserve from 2008 to 2015. In-depth semistructured interviews were conducted in two contrasting, but representative, villages, where traditional mixed-crop farming was being replaced by cash crops such as coffee, maize, and cotton. Access to state-subsidized food supply and increase in cash income through wage labor, coupled with increasing depredation of food crops by wild animals, were some causes for the shift to cash crops. Declining supply of non-timber forest produce (NTFP) and the subsistence cash it provided has also impacted farmer livelihoods and indirectly contributed to this shift. The changing aspirations of younger Soligas and inadequate state support for mixed-crop farming also could be contributing factors. Soligas consistently maintained that increased wildlife depredation of food crops, reduction in supplies of wild foods, and the decline in NTFP was due to poor forest health. The transition to cash crops improved cash flows but exposed the Soligas to market risks. While food security also improved, the nutritional quality of diet declined. Soligas are adopting new farming practices, diets, and livelihood strategies, and importantly, leveraging rights historically denied to them, all a reflection of their social resilience.
Although wildfire plays an important role in maintaining biodiversity in many ecosystems, fire management to protect human assets is often carried out by different agencies than those tasked for conserving biodiversity. In fact, fire risk reduction and biodiversity conservation are often viewed as competing objectives. Here we explored the role of management through private land conservation and asked whether we could identify private land acquisition strategies that fulfill the mutual objectives of biodiversity conservation and fire risk reduction, or whether the maximization of one objective comes at a detriment to the other. Using a fixed budget and number of homes slated for development, we simulated 20 years of housing growth under alternative conservation selection strategies, and then projected the mean risk of fires destroying structures and the area and configuration of important habitat types in San Diego County, California, USA. We found clear differences in both fire risk projections and biodiversity impacts based on the way conservation lands are prioritized for selection, but these differences were split between two distinct groupings. If no conservation lands were purchased, or if purchases were prioritized based on cost or likelihood of development, both the projected fire risk and biodiversity impacts were much higher than if conservation lands were purchased in areas with high fire hazard or high species richness. Thus, conserving land focused on either of the two objectives resulted in nearly equivalent mutual benefits for both. These benefits not only resulted from preventing development in sensitive areas, but they were also due to the different housing patterns and arrangements that occurred as development was displaced from those areas. Although biodiversity conflicts may still arise using other fire management strategies, this study shows that mutual objectives can be attained through land-use planning in this region. These results likely generalize to any place where high species richness overlaps with hazardous wildland vegetation.
Seedling establishment is a critical step that may ultimately govern tree species’ distribution shifts under environmental change. Annual variation in the location of seed rain and microclimates results in transient “windows of opportunity” for tree seedling establishment across the landscape. These establishment windows vary at fine spatiotemporal scales that are not considered in most assessments of climate change impacts on tree species range dynamics and habitat displacement. We integrate field seedling establishment trials conducted in the southern Sierra Nevada and western Tehachapi Mountains of southern California with spatially downscaled grids of modeled water-year climatic water deficit (CWDwy) and mean August maximum daily temperature (Tmax) to map historical and projected future microclimates suitable for establishment windows of opportunity for Quercus douglasii, a dominant tree species of warm, dry foothill woodlands, and Q. kelloggii, a dominant of cooler, more mesic montane woodlands and forests. Based on quasi-binomial regression models, Q. douglasii seedling establishment is significantly associated with modeled CWDwy and to a lesser degree with modeled Tmax. Q. kelloggii seedling establishment is most strongly associated with Tmax and best predicted by a two-factor model including CWDwy and Tmax. Establishment niche models are applied to explore recruitment window dynamics in the western Tehachapi Mountains, where these species are currently widespread canopy dominants. Establishment windows are projected to decrease by 50–95%, shrinking locally to higher elevations and north-facing slopes by the end of this century depending on the species and climate scenario. These decreases in establishment windows suggest the potential for longer-term regional population declines of the species. While many additional processes regulate seedling establishment and growth, this study highlights the need to account for topoclimatic controls and interannual climatic variation when assessing how seedling establishment and colonization processes could be affected by climate change.
Brown, M. 2015. Creating Useful and Usable Climate Tools for Sagebrush Land Management Through Scientist and Manager Collaboration, Oregon State University thesis. http://hdl.handle.net/1957/56343
The sagebrush ecosystem, home to numerous plant and animal species including big sagebrush (Artemisia tridentata) and the endemic greater sage-grouse (Centrocercus urophasianus), has endured fragmentation and degradation of both quantity and quality due to the cumulative and synergistic relationships between an abundance of individual disturbances including grazing, invasive annuals and fire. Climate change may now be an additional threat that poses the greatest risk to these imperiled habitats. Natural resource agencies such as the Bureau of Land Management (BLM) seek to conserve sagelands through land management activities that ensure the survival of sage-grouse and continuity of the sagebrush biome. Web-based climate tools can help convey climate information that may be necessary for long-term land management, but these tools may not agree with the needs of land managers, may be too complex, or may be misinterpreted. To overcome barriers of user compatibility, the participation of both climate scientists and land managers is necessary during tool development. With the collaboration of Oregon and Idaho BLM sagebrush land managers and climate scientists, this study sought to assess land manager needs and define the criteria for useful and useable climate tools. Using an initial online survey, individual phone interviews with land managers, and a follow-up online survey, a series of land management activities and related climate variables were identified, and several web-based climate tools were assessed. Most managers perform vegetation management through a variety of means including seeding and herbicide application. Such activities are affected by the magnitude and timing of precipitation and temperature, as well as other variables, on seasonal and annual timeframes. For planning purposes land managers also need information on long-term 10-20 year climate trends. The act of listening to the needs of land managers uncovered communication barriers, and provided feedback on existing climate tools emphasizing accessibility, dependability and consistency, clear explanation of terminology, effective visualizations, and relevant spatial and temporal scales to the scope of management activities. We also identified a need for basic information and education on the location of existing climate tools and climate impacts, and a need for near-term forecasting tools that could bridge the gap between weather (≤ 6 months) and climate (≥ 30 years) projections.
Terra Magazine, Oregon State University’s research magazine, featured Brown’s research.
The dynamic global vegetation model (DGVM) MC2 was run over the conterminous US at 30arc sec (~800m) to simulate the impacts of nine climate futures generated by 3GCMs (CSIRO, MIROC and CGCM3) using 3 emission scenarios (A2, A1B, B1) in the context of the LandCarbon national carbon sequestration assessment. It first simulated potential vegetation dynamics from coast to coast assuming no human impacts and naturally occurring wildfires. A moderate effect of increased atmospheric CO2 on water use efficiency and growth enhanced carbon sequestration but did not greatly influence woody encroachment. The wildfires maintained prairie-forest ecotones in the Great Plains. With simulated fire suppression, the number and impacts of wildfires was reduced since only catastrophic fires were allowed to escape. This greatly increased the expansion of forests and woodlands across the western US and some of the ecotones disappeared. However, when fires did occur their impacts (both extent and biomass consumed) were very large. We also evaluated the relative influence of human land use including forest and crop harvest by running the DGVM with land use (and fire suppression) and simple land management rules. From 2041 through 2060, carbon stocks (live biomass, soil and dead biomass) of US terrestrial ecosystems varied between 155 and 162 Pg C across the three emission scenarios when potential natural vegetation was simulated. With land use, periodic harvest of croplands and timberlands as well as the prevention of woody expansion across the West reduced carbon stocks to a range of 122-126 Pg C while effective fire suppression reduced fire emissions by about 50%. Despite the simplicity of our approach, the differences between the size of the carbon stocks confirm other reports of the importance of land use on the carbon cycle over climate change.
Climate change adaptation and mitigation require understanding of vegetation response to climate change. Using the MC2 dynamic global vegetation model (DGVM) we simulate vegetation for the Northwest United States using results from 20 different Climate Model Intercomparison Project Phase 5 (CMIP5) models downscaled using the MACA algorithm. Results were generated for representative concentration pathways (RCPs) 4.5 and 8.5 under vegetation modeling scenarios with and without fire suppression for a total of 80 model runs for future projections. For analysis, results were aggregated by three subregions: the Western Northwest (WNW), from the crest of the Cascade Mountains west; Northwest Plains and Plateau (NWPP), the non-mountainous areas east of the Cascade Mountains; and Eastern Northwest Mountains (ENWM), the mountainous areas east of the Cascade Mountains. In the WNW, mean fire interval (MFI) averaged over all climate projections decreases by up to 48%, and potential vegetation shifts from conifer to mixed forest under RCP 4.5 and 8.5 with and without fire suppression. In the NWPP MFI averaged over all climate projections decreases by up to 82% without fire suppression and increases by up to 14% with fire suppression resulting in woodier vegetation cover. In the ENWM, MFI averaged across all climate projections decreases by up to 81%, subalpine communities are lost, but conifer forests continue to dominate the subregion in the future.