Spatial Analysis For Conservation and Sustainability
Fire
Fire is now lacking in many ecosystems that require it, yet fire is also a dire threat to lives, homes, and livelihoods. Due to climate and land use change, fire frequency has risen in recent decades, and we study how societies and communities can better live with fire, and where to restore fire regimes.
Identifying areas of the wildland-urban interface (WUI) that are prone to severe wildfire is an important step in prioritizing fire prevention and preparedness projects. Our objective is to determine at a regional scale the relative risk of severe wildfire in WUI areas and the numbers of people and houses in high-risk areas. For a study area in northern lower Michigan, we first develop a spatial database of WUI areas (both intermix and interface) using housing data from the 2000 US Census and 1994 vegetation data from the Gap Analysis Project of the Michigan Department of Natural Resources. Then, we develop a spatial database of historic (pre-1900) fire regimes and current (1994) fuels to identify areas with high risk of standreplacing fires. High-risk areas historically supported jack pine (P. banksiana Lamb.) and mixed pine forests with stand-replacing fire rotations less than 100 years and currently support upland conifer and hardwood forests. Analysis of the databases shows that 26% of the study area is WUI. About 25% of the WUI has relatively high fire risk. Over 88% of the WUI with high fire risk has low housing density (<1 house per 2 ha) and is classified as intermix where fuels and structures intermingle. The predominance of high-risk intermix areas with low-density housing has implications for planning effective fuel treatments and evacuation plans.
Fire is an important natural disturbance process in arid grasslands but current fire regimes are largely the result of both human and natural processes and their interactions. The collapse of the Soviet Union in 1991 spurred substantial socioeconomic changes and was ultimately followed by a rapid increase in burned area in southern Russia. What is unclear is whether this increase in burned area was caused by decreasing livestock numbers, vegetation changes, climate change, or interactions of these factors. Our research goal was to identify the driving forces behind the increase in burned area in the arid grasslands of southern Russia. Our study area encompassed 19,000 km2 in the Republic of Kalmykia in southern Russia. We analyzed annual burned area from 1986 to 2006 as a function of livestock population, NDVI, precipitation, temperature, and broad-scale oscillation indices using best subset regressions and structural equation modeling. Our results supported the hypothesis that vegetation recovered within 5-6 years after the livestock declined in the beginning of the 1990s, to a point at which large fires could be sustained. Climate was an important explanatory factor for burning, but mainly after 1996 when lower livestock numbers allowed fuels to accumulate. Ultimately, our results highlight the complexity of coupled human-natural systems, and provide an example of how abrupt socioeconomic change may affect fire regimes.
Wildland fire is a major concern in the wildland-urban interface (WUI), where human structures intermingle with wildland vegetation. Reducing wildfire risk in the WUI is more complicated than in wildland areas, owing to interactions between spatial patterns of housing and wildland fuels. Fuel treatments are commonly applied in wildlands surrounding WUI communities. Protecting the immediate surroundings of structures and building with fire-resistant materials might be more effective, but limited resources and uncooperative homeowners often make these impractical. Our question was how to allocate fuel treatments in the WUI under these constraints. We developed an approach to allocate fuel breaks around individual or groups of structures to minimise total treatment area. Treatment units were ranked according to their housing density and fire risk. We tested this method in a Wisconsin landscape containing 3768 structures, and found that our treatment approach required considerably less area than alternatives (588 v. 1050 ha required to protect every structure independently). Our method may serve as a baseline for planning fuel treatments in WUI areas where it is impractical to protect every single house, or when fire-proofing is unfeasible. This approach is especially suitable in regions where spotting is a minor cause of home ignitions.
Fire simulation studies that use models such as FARSITE often assume that ignition locations are distributed randomly, because spatially explicit information about actual ignition locations are dif ? cult to obtain. However, many studies show that the spatial distribution of ignition locations, whether human- caused or natural, is non-random. Thus, predictions from ? re simulations based on random ignitions may be unrealistic. However, the extent to which the assumption of ignition location affects the predictions of ? re simulation models has never been systematically explored. Our goal was to assess the difference in ? re simulations that are based on random versus non-random ignition location patterns. We conducted four sets of 6000 FARSITE simulations for the Santa Monica Mountains in California to quantify the in ? uence of random and non-random ignition locations and normal and extreme weather conditions on ? re size distributions and spatial patterns of burn probability. Under extreme weather conditions, ? res were signi ? cantly larger for non-random ignitions compared to random ignitions (mean area of 344.5 ha and 230.1 ha, respectively), but burn probability maps were highly correlated (r = 0.83). Under normal weather, random ignitions produced signi ? cantly larger ? res than non-random ignitions (17.5 ha and 13.3 ha, respectively), and the spatial correlations between burn probability maps were not high (r = 0.54), though the difference in the average burn probability was small. The results of the study suggest that the location of ignitions used in ? re simulation models may substantially in ? uence the spatial predictions of ? re spread patterns. However, the spatial bias introduced by using a random ignition location model may be minimized if the ? re simulations are conducted under extreme weather conditions when ? re spread is greatest.
Fire and wetlands are not concepts that we intuitively think about in conjunction with one another. Masters student Colleen Sutheimer is working to change that with the hope that her work will eventually inform future wetland management and conservation on a broad scale. By reconstructing the historic temporal and spatial scale of fires in forested wetlands in the upper Great Lakes region, Sutheimer believes her work will help managers make good decisions about the use of fire as a management tool in these extremely unique and important ecosystems.
Forested wetlands make up almost half of all freshwater wetlands in the United States, and forested wetlands declined by over 250,000 hectares between 2004 and 2009 alone. These areas are extremely important ecologically, though, as they are home to many unique plant and animal species, are important stores of organic carbon, and provide water filtration services. However, the historic role of fire in these systems is not well understood. Specifically, whether these systems developed with fire and how often fire happened in the past are questions Sutheimer is hoping to answer. “This is a really interesting time to be working on fire in the Great Lakes region, but especially in these wetland systems. A rigorous understanding of fire’s role in Wisconsin has not been achieved yet,” Sutheimer said of her research.
An example of a processed and dated remnant red pine stump. This tree originated in 1718 and was harvested around the 1850s. Each date corresponds to a different fire that scarred the tree while it was still alive.
Reconstructing historic fire regimes is not an easy job, however. In order to do it, Colleen and her colleagues at Wisconsin DNR target red pine stumps in forested wetlands that are remnants from the clear cut that took place over northern Wisconsin and the Upper Peninsula of Michigan in the 1800s. Using chainsaws, Sutheimer takes samples from these stumps and non-destructive samples from living trees and snags. These collected samples must then be dried, planed to create a flat surface, and finally sanded to smooth the surface and make the growth rings visible and ready for analysis. With a well-prepared sample, Sutheimer can determine the age of the tree, as well as examine fires scars as evidence of fire exposure in the growth rings of the tree. Targeting these old stumps allows Sutheimer to examine the frequency and intensity of fires that occurred up to 500 years in the past. Additionally, by taking samples at a large spatial scale, Sutheimer can get an idea of how intense specific fires were.
Sutheimer has already completed sampling at one of her study sites, near Betchler Lake in the Hiawatha National Forest, located in the upper peninsula of Michigan. At this site alone, Sutheimer took over 80 samples from both the periphery of the wetland as well as from “islands” of trees within the wetland. Using the samples she has collected from the Betchler Lake Area, Sutheimer will be able to reconstruct an entire fire history for this localized wetland area. Though Sutheimer has not aged these samples yet, a sample from another area yielded a tree that had originated in the 1500s, making Sutheimer optimistic that their sampling will successfully span a broad temporal range. This site is just the beginning. Sutheimer has plans to reconstruct fire histories for additional sites in the Hiawatha, Ottawa, and Chequamegon-Nicolet National Forests, giving her an unprecedented look at the history of fire in these wetland systems.
Location of where red pine stumps were sampled and peatland cores were taken within and around the Betchler Lake site.
Disturbances such as fire may be important shapers of forested wetlands by helping to stop vegetation encroachment and allowing them to continue to provide essential habitat to many amphibian and carnivorous plant species that are already threatened by other factors. These areas also serve as carbon sinks by storing carbon both in the trees and in the inundated organic soils. Threats like climate change make it even more imperative to understand past disturbance regimes to help scientists plan for future climate scenarios. Understanding the historic role and characteristics of the fire regime in these systems will allow Sutheimer not only to understand how fire has affected these systems in the past, but to provide recommendations for its use as a management tool in the future.
The wildland–urban interface (WUI) is the area where houses meet or intermingle with undeveloped wildland vegetation. The WUI is thus a focal area for human– environment conflicts, such as the destruction of homes by wildfires, habitat fragmentation, introduction of exotic species, and biodiversity decline. Our goal was to conduct a spatially detailed assessment of the WUI across the United States to provide a framework for scientific inquiries into housing growth effects on the environment and to inform both national policymakers and local land managers about the WUI and associated issues. The WUI in the conterminous United States covers 719 156 km2 (9% of land area) and contains 44.8 million housing units (39% of all houses). WUI areas are particularly widespread in the eastern United States, reaching a maximum of 72% of land area in Connecticut. California has the highest number of WUI housing units (5.1 million). The extent of the WUI highlights the need for ecological principles in land-use planning as well as sprawl-limiting policies to adequately address both wildfire threats and conservation problems.
Federal wildland fire policy in the United States has been substantially revised over the past 10 years and new emphasis has been given to the wildland– urban interface (WUI), which creates a need for information about the WUI’s location and extent. We operationalized a policy definition published in the Federal Register (US Department of the Interior [USDI] and US Department of Agriculture [USDA]), 2001, Urban wildland interface communities within vicinity of federal lands that are at high risk from wildfire. Fed. Regist. 66(3):751–777) to create national maps and statistics of the WUI to guide strategic planning. Using geographic information system analysis, we evaluate the national WUI by altering the definition’s parameters to assess the influence of individual parameters (i.e., housing density, vegetation type and density, and interface buffer distance) and stability of outcomes. The most sensitive parameter was the housing density threshold. Changes in outputs (WUI homes and area) were much smaller than parameter variations suggesting the WUI definition generates stable results on most landscapes. Overall, modifying the WUI definition resulted in a similar amount of WUI area and number of homes and affected the precise location of the WUI.
The wildland-urban interface (WUI) is the area where houses and wildland vegetation meet or intermingle, and where wildfire problems are most pronounced. Here we report that the WUI in the United States grew rapidly from 1990 to 2010 in terms of both number of new houses (from 30.8 to 43.4 million; 41% growth) and land area (from 581,000 to 770,000 km2; 33% growth), making it the fastest-growing land use type in the conterminous United States. The vast majority of new WUI areas were the result of new housing (97%), not related to an increase in wildland vegetation. Within the perimeter of recent wildfires (1990–2015), there were 286,000 houses in 2010, compared with 177,000 in 1990. Furthermore, WUI growth often results in more wildfire ignitions, putting more lives and houses at risk. Wildfire problems will not abate if recent housing growth trends continue.
Wildfires are a major threat to houses and people in the US. About 2 billion dollars are spent every year in preventing and suppressing fires by the US Forest Service alone, and about 1,300 houses are burned each year on average. Housing is expanding every year and the number and frequency of wildfires in increasing as well, suggesting that this problem is likely to get worse in the future. Understanding the how wildfires affect houses, and what we can do to prevent those damages, is key to guide land-use planning and management efforts in fire prone places.
Cedar Fire in San Diego, CA in 2003, study area layout.Four Mile Fire in Boulder, CO in 2010, study area layout.
“People want nice views and to live out in the country, however, houses in such locations are under high risk of wildfires”, said Patricia Alexandre, a PhD student at Silvis. Understanding the factors that explain the likelihood of a house to burn during a wildfire is of major need for land-use planning in wildfire prone areas, and for agencies such as the US Forest Service. However, there is little knowledge on this topic according to Patricia. Patricia’s research focuses on identifying the key factors that explain the likelihood of a house to burn during a fire. For this, she is using two wildfires as case studies, including a wildfire that occurred in San Diego (California) and one in Boulder (Colorado). High resolution imagery before and after the fire is being used to map all the houses within those fires, that burned due to the fires. ‘In the Boulder fire for example, we mapped about 1100 houses, and we see that 10% of them were burned after the fire’, Patricia said.
The study explores about 40 environmental variables to predict the likelihood of a house to burn, such as vegetation conditions, topography (aspects, slope, elevation, topographic position), and the spatial arrangement of house (housing density, distance to near house). According to Patricia, predicting the likely of a house to burn is a complex task. “In Colorado, the houses most likely to burn were those on high slopes or on top of ridges, as well as those located at the edges of the neighborhoods. In San Diego, however, the results were more variable. What might explain things in one fire may not work in other.”
Another important finding from this study is that the spatial arrangement of the houses matters. According to Patricia, “previous efforts used only topography and spatial arrangement to predict the likelihood of a house to burn given a wildfire, but we decided to add vegetation to see how much in fact is vegetation contributing to this phenomenon. We see that vegetation alone cannot explain why a house burned alone, the way houses are arranged on the land is also important”. Currents efforts are focused towards refining the models so to have a better understanding of the local forces that result in burned houses within a single fire. However, the ultimate goal is to expand the study to the whole US.Patricia hopes that this study will help the government to allocate resources (e.g. fuel management) in a more efficient manner, and will provide land-use planners, urban planners, and home owners with useful information and recommendations about housing construction in wildfire-prone areas. This study is a step towards Patricia’s dissertation focused on understanding the factors that explain house loss to wildlife in the US. “My ultimate goal is to develop a risk map for the whole US that tells you how likely it is that your house burns if a fire occurs”, Patricia said.
Imagine an expansive prairie, dotted with Bur Oak trees, leaves swaying in the afternoon breeze. Bison were common in this scene, along with other vestiges of a time’s past. When Euro-Americans first settled southern Wisconsin, over 150 years ago, this is more or less what they found. However, with settlement came changes in land use, resulting in changes in land cover. The prairies and oak savannas with their rich and deep soils were converted to agriculture, urban areas sprouted, and natural disturbances, most notably fire, which were necessary to maintain the structure of the vegetation communities, were suppressed. As a result, the expansive prairies and oak savannas of Southern Wisconsin were nearly wiped from the map.
Prescribed fires, like this one at Muralt Bluff Prairie State Natural Area, help biologists restore and maintain prairies and grasslands in key locations around Wisconsin. Photo by Tallgrass Prairie and Oak Savanna Fire Science Consortium.
Fast-forward 150 years, and resources managers throughout Wisconsin are challenged to restore these once common habitats. The most effective approach is prescribed fire. Prescribed fires re-create natural burns in a safe and controlled manner. Fire is critical for knocking back woody vegetation, replenishing the soil, allowing certain plants to sprout or reproduce, and shaping the structure and composition of the habitats, which directly impact wildlife communities. Because prairie and oak savanna used to be expansive, covering most of southern Wisconsin, there are many lands today that need fire to maintain the character of the native habitats. Yet, this poses a different challenge. Resource managers have finite funds and personnel for applying prescribed fire. With so many lands that would benefit from fire, and limited resources to conduct prescribed fires, there is a real need to better understand where priorities lie. To achieve this, Sarah and Dave, along with collaborators from the Tallgrass Prairie and Oak Savanna Fire Science Consortium, are using an approach that considers the potential ecological gains of applying prescribed fire along with the effort needed to burn a given area and the ease with which managers are likely to be able to apply prescribed fire in a particular landscape.
Prescribed fire is an important tool for managing fire-dependent natural communities, like these oak barrens found at Quincy Bluff and Wetland State Natural Area. Photo by Tallgrass Prairie and Oak Savanna Fire Science Consortium
The group is piloting this approach in Wisconsin, but is hoping that it may be more broadly applied across the region, and possibly in other regions, in the future. ‘Prescribed fire is a critical management tool for many landscapes in the US. Given limited resources, it is important to be able to use this tool strategically to achieve the greatest possible gains for our conservation dollars,’ says Sarah. To that end, the group is relying heavily on free, publically available datasets (e.g., Landfire vegetation data, Wildlife Action Plans, and Wildland-Urban Interface housing data), and common sense approaches to prioritization. ‘It is really important to us that others to be able to understand and apply this approach in their own landscapes. Many land management agencies and conservation organizations are working very hard to conserve, manage, and restore our native landscapes. The work is time consuming, complex and often expensive. We want to provide these managers with practical tools that can help them decide where they can get the greatest benefits from their efforts.'”
