Tag Archives: threatened

Viewing biodiversity through the ecoregional lens

The Nature Conservancy’s Atlas of Global Conservation is a fabulous resource for understanding biological diversity. Scientists have divided up the world into more than 1,000 ecoregions and analyzed how they compare across dozens of measures.

I’ve used data from TNC’s atlas to create a slide deck that illustrates patterns in species richness and threats to biodiversity, with a focus on the United States and American West. Below is a video of the PowerPoint, which you can download at the bottom of this post.

Visualizing biodiversity through the lens of ecoregions from EcoWest on Vimeo.

Biome basics

Before we get to ecoregions, let me first note a broader way that TNC and others classify the natural world: biomes. An area’s climate more or less determines what types of plants can grow, and at the highest level we can classify the planet’s land masses according to the predominant vegetation, or lack thereof. There are 16 terrestrial biomes, ranging from snow and tundra to tropical forests.

The map below (click to enlarge) shows the biomes found in the United States. Much of the interior West is dominated by desert and xeric (dry) shrublands, but the higher elevations support temperate conifer forests. California has Mediterranean forests along much of its coast and the Sierra Foothills. There’s a bit of subtropical forest in the mountains of Southeast Arizona and temperate broadleaf forest in Oregon’s Coastal Range.

United States biomes

As with temperature, rainfall, and elevation, there is more uniformity in the biomes found in the East than the West. Look, for example, at how many different types of communities are found in California, or how isolated mountains in the Great Basin create little biome islands.

The United States actually leads the world in the number of biomes and smaller ecoregions within its borders, even exceeding countries that are much larger in size, as shown in the graphic below.

United States biomes and ecoregions

So it’s no surprise that the United States also ranks high in species diversity. In the graphic below, blue bars show the number of species by type. Orange diamonds show what percent of the world’s species are found in the United States and the number in parenthesis in the labels indicate the U.S. ranking worldwide. The highest levels of diversity for several groups are found in the United States, including freshwater mussels, freshwater snails, and crayfishes; several other groups, such as freshwater fishes and gymnosperms, are also well represented here.

United States ranks high in species diversity

Analyzing ecoregions

A more fine-grained view than biomes classifies the terrestrial world into 825 unique ecoregions. These areas are sort of like ecological neighborhoods with similar habitat. Below is a close-up of the American West. If you were to drive through several ecoregions on an interstate road trip, you’d notice the differences simply by looking out the window.

Ecoregions of the American West

TNC’s atlas also analyzes the planet according to its 426 freshwater ecoregions. Each of the regions has a unique collection of aquatic species and freshwater habitats. The map below shows the West’s two-dozen or so freshwater ecoregions, which generally correspond to the boundaries of important river basins.

Freshwater ecoregions of the American West

Dozens of biodiversity metrics

TNC’s atlas offers dozens and dozens of layers of geographic information by terrestrial, freshwater, and marine ecoregion. The deck that you can download at the bottom of this post has 71 slides, with views of both the world and United States.

To give you a taste of what’s available, here’s a summary of three slides.

1) Species diversity is greatest around the equator

One way to describe biodiversity is to look at the evolutionary distinctiveness of species in a given location. The map below shows the phylogenetic diversity of terrestrial vertebrate species (animals with a backbone). Phylogenetics is a measure of how closely related a group of species is. An ecoregion with high phylogenetic diversity has species that are more distinct from one another (see this summary and this paper for more on the measure).

In general, measures of species diversity are greater at lower latitudes due to the past effects of Ice Age glaciation at higher latitudes and the configuration of islands and other landforms on the Earth, both past and present. In the West, phylogenetic diversity of vertebrate species tends to be highest in the desert Southwest.

Phylogenetic diversity of species

2) Hotspots for threatened animals 

The analysis and conservation of biodiversity often focuses on those species most at risk of extinction. The map below shows the number of globally threatened animals by terrestrial ecoregion. Threatened species are those listed by the International Union for the Conservation of Nature’s Red List as vulnerable, endangered, or critically endangered. Globally, some of the greatest concentrations of threatened vertebrates are in South America and Southeast Asia. About half of the threatened animals are reptiles and amphibians, one quarter are mammals, and one quarter are birds. In the United States, the Southwest, the foothills around California’s Central Valley, the Southeast, and the Appalachians have the most threatened animals.

Number of globally threatened animals

3) Plenty of plants in arid American West

The map below shows the number of plant species by terrestrial ecoregion. Worldwide, there are more than 420,000 of the so-called higher order plants: trees, vines, grasses, fruits, vegetables, and legumes. Deserts and arid lands typically have fewer plant species, while tropical rainforests have the most. But in North America, some drier parts of the inland West actually have more plant species than wetter climes along the coast. Compare, for example, the Great Basin in Nevada to Washington.

Number of plant species

Those are just a few of the slides that I found most interesting. I’d be curious to hear from readers if they spot other patterns.

Data sources

To create the maps, I downloaded the GIS data from Data Basin (a search query for “Hoekstra,” as in atlas lead author and EcoWest advisor Jon Hoekstra, will return all the layers).

I highly recommend the book form of TNC’s atlas, which taught me a ton about biodiversity around the globe.

See this page for more background on ecoregions from WWF.


Download Slides: TNC Conservation AtlasDownload Slides: TNC Conservation Atlas (54.77 MB pptx)
Download Notes: TNC Conservation AtlasDownload Notes: TNC Conservation Atlas (5.18 MB pdf)

EcoWest’s mission is to analyze, visualize, and share data on environmental trends in the North American West. Please subscribe to our RSS feed, opt-in for email updates, follow us on Twitter, or like us on Facebook.

Counting homes in the Western WUI

When firefighters are deployed to battle wildfires, they often focus on saving structures in the wildland-urban interface (WUI), where homes mix with or border flammable vegetation.

Where are these vulnerable homes located in the West?

Data from analytics firm CoreLogic provide a good high-level overview of the Western WUI. I’ve created a dashboard on this page to summarize their numbers.

CoreLogic uses four categorizes to describe the risk of wildfires destroying residential properties: very high, high, moderate, and low. There are also categories for agricultural and urban properties, which are not rated for their fire danger.

In the 13 Western states it analyzed, CoreLogic found some 740,000 residences at high or very high risk for wildfire damage and those homes are valued at more than $136 billion. Nearly 168,000 homes, valued at more than $32 billion, are in the very high risk category.

Geographic disparities

Below are a couple of views of the data (click to enlarge). The map shows the number of homes in the very high risk category, with the circles colored by the percent of homes in each state that are in this most vulnerable category. You can see that California and Colorado both have nearly 50,000 homes in this category, but while that’s about 3 percent of Colorado’s residential properties, it’s just 0.5 percent of California’s. The bar chart shows what percent of each state’s homes are in the very high and high categories.

EcoWest WUI homes dashboard

New Mexico, Montana, and Colorado have the highest percentages of homes in the top-two risk categories. Below is another visualization of the data, which just focuses on the very high risk category.

Number of residential properties facing very high risk

Comparing average home values

CoreLogic also provides data on the value of the residential properties in each of the risk categories. I divided these values by the number of homes in each category to create an average value figure, which is presented below in a scatter plot.

In this graphic, I’m comparing the very high risk to the low risk homes. The circles vary in size by the number of homes in the very high risk category and they’re colored to show the percent of homes in a state that are in this most vulnerable subset. If a state is above the 45-degree line, its very high risk properties are more valuable, on average, than the low risk homes, and vice versa.

Comparing values of properties in Western WUI

This scatter plot shows that in plenty of Western states, homes in the riskiest and least risky categorize have roughly the same average value (they fall on or close to the 45-degree line). But in Nevada, the very high risk homes have an average value of about $325,000, while the lowest risk houses have an average value of about $165,000. The spread of the circles also indicates that there’s great state-to-state variation in home values. Colorado’s very high risk properties, for example, are more than twice as valuable as those in Texas.

CoreLogic sells much more detailed information on risk to insurance companies, but these state-level figures still show some interesting geographic patterns. California, Colorado, and Texas have the most homes in the WUI, while Washington, Wyoming, Nevada, Utah, and Oklahoma have very few.

Here’s more from CoreLogic and Dr. Howard Botts, its vice president and director of database development:

The Wildland Urban Interface (WUI) identifies the intersection of potentially high-risk fire areas and large numbers of homes. The report states that just between the years of 1990 to 2008, there were close to 17 million new homes built in the U.S., of which 10 million (58 percent) were located in the WUI and therefore potentially located near high wildfire risk zones. “Homes located within a city boundary are not safe from the threat of wildfire destruction. In fact, the unprecedented growth of urban areas over the past 50 years has generally increased the likelihood homes will be damaged by wildfire activity,” said Botts. “As residential development has expanded into formerly undeveloped wildlands, the transitional area between the two, known as the Wildfire Urban Interface, has become exceptionally vulnerable to wildfire. Approximately 40 percent of homes in the U.S. are located in that zone, and wind-blown embers are capable of igniting homes located hundreds, or even thousands of feet away from an actual fire.”

I’d be curious if readers see any other patterns in the data, which is available for download below. We have a gallery of state-by-state WUI maps and some more discussion of the issue in this post.

NOTE: I’m about to head off on vacation, so EcoWest will resume with new posts the week of July 15.


Download Slides: CoreLogic WUI HomesDownload Slides: CoreLogic WUI Homes (1.1 MB pptx)
Download Data: CoreLogic WUI HomesDownload Data: CoreLogic WUI Homes (43.7 kB xlsx)

EcoWest’s mission is to analyze, visualize, and share data on environmental trends in the North American West. Please subscribe to our RSS feed, opt-in for email updates, follow us on Twitter, or like us on Facebook.