Land development is a major threat to cismontane ecosystems. As the California population grows, more and more cismontane land is cleared for human use. Coastal sage scrub communities are now rare enough to be considered an endangered habitat. Much of the remaining coastal sage scrub communities are found on private land, therefore they are not protected by federal or state parks. Land development has also left the remaining communities very fragmented, leading to further degradation. Remaining cismontane habitats are composed of isolated patches surrounded by urbanization. It is predicted that fragments smaller than 1 square kilometer will lose their native vertebrate species in the near future. Development near these ecosystems also increases exposure to pollution, which has been shown to reduce native coastal species cover. Finally, increased development near these habitats increases the frequency of man-made fires that further threaten the ecosystem.

Human presence has increased the frequency and intensity of cismontane fires

Although cismontane ecosystems are adapted to fire, they naturally occur once every few decades. Development has led to frequent man-made fires through incidences such as power line failures. Additionally, the invasive species that now cover many cismontane communities are more prone to intense fires. These intense fires then disturb the area so that more invasives can spread and the cycle is exacerbated.

Changes in the fire regime lead to habitat type conversion

Fire regimes vary between the different chaparral and coastal sage communities, but researchers found that fire periods of less than 30 years overall decrease habitat health. When the fire regime is altered, it leads to significant alterations to the habitat and plant species composition. This change from one habitat to another is called a habitat type conversion. Cismontane habitats typically convert to non-native grasses, like in this picture of a chaparral habitat in San Diego.

Too many fires decrease biodiversity!

As fires in these communities become more intense, they create homogeneous landscapes- areas that are all in the same stage of recovery. Part of the reason chaparral habitats are so diverse is because fire traditionally created a heterogeneous environment- where different areas were in different stages of maturity so they could support different species of wildlife. In the picture to the left, a chaparral habitat off of State Highway 78 has experienced too many fire disturbances and is now a homogeneous landscape, covered in invasive weeds.

Prescribed fires can cause more harm to the ecosystem

Chaparral habitats are already threatened by too much fire so prescribed burning is not an effective tool for management. Additionally, if the fires are started in seasons other than the natural fire season, the burning will cause serious damage to native species and encourage type conversion. Finally, prescribed burning can accidentally spread and harm nearby communities, such as the Creek Fire of 2012 (pictured to the right).

Livestock graze away native vegetation and their hooves disturb and compact the soil.

Grazers also contribute to the spread of invasive species by carrying invasive seeds on their hooves. Although some grazing may be beneficial because it stimulates new growth, heavy grazing leads to habitat type conversion and overall reduction of native species cover.

Climate change is expected to bring more disturbance to cismontane ecosystems.

In fact, as shown in the picture, significant areas of chaparral are expected to be replaced by non-natives if climate change continues at the same rate.

Climate change will affect the distribution of cismontane ecosystems further as more changes to the fire regime continue with increased disturbance from severe drought and invasive species.