Connecting Mountain Islands in the Desert

Saving bighorn sheep in the Soda Mountains

From the perspective of a bighorn sheep, mountain ranges in the Mojave Desert are island oases of habitat amid seas of lowland desert. The seas are exposed, hot and lacking in water and resources, while desert mountain ranges support lush microclimates, seeps, springs, and food sources. Yet, as herds of bighorn sheep expand, they outgrow their mountain island. Eventually a herd will split and some sheep will migrate across the open lowlands to colonize a new mountain range. This pattern of growth, splitting and migration is essential to maintaining a healthy population of bighorn sheep in the desert. The genetic mixing that happens when herds split, migrate and colonize new areas ensures that the population remains resistant to disease.

The herds of bighorn sheep that call the California desert home have been growing and expanding to new mountain ranges – a good thing, considering the population is only 10% of what it once was. This is partially due to the efforts of various scientists, non-profit groups and the National Park Service, all of whom are making protection of habitat and migration pathways for bighorn sheep a priority in California. The California Desert Protection Act of 1994 established the 1.6 million acre Mojave Preserve and designated Joshua Tree and Death Valley as national parks. Recently, bighorn sheep living in the mountain island of the Cady Mountains and Afton Canyon crossed a 15-mile sea of lowlands to re-colonize the unoccupied habitat of the South Soda Mountains, an area that is partially protected by the Mojave National Preserve.

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As the herd in the South Soda Mountains grows (a good thing!), they will need to move further north into the North Soda Mountains, the Avawatz Mountains and eventually Death Valley. This will be challenging for the herd because a major highway, I-15, cuts across the lowlands between the South and North Soda Mountains. And even more problematic than the highway is the fact that the BLM is moving forward with a large-scale solar energy development project – the Soda Mountains Solar project – that would make movement to the north next to impossible for the sheep. Conservation scientists who have been trying to figure out how to help sheep to cross I-15 say that a project in this location would undermine all of their efforts to connect island mountains and maintain a healthy population of sheep desert-wide.

For almost five years, Defenders has objected to a large-scale solar facility in this area because it would eliminate the possibility of restoring connective pathways for the Mojave desert bighorn sheep population. This region is also occupied desert tortoise and kit fox habitat, and is directly adjacent to the Mojave National Preserve – one of the most significant land conservation successes in our country. When it comes to solar energy, Defenders does not take decisions regarding where projects are located lightly. We strongly support transitioning to a carbon-free electricity generation system, but only if it is “smart from the start” and avoids impacts to imperiled wildlife and special places. We critically analyze each project proposed, and the Soda Mountain Solar project doesn’t meet the standard of smart from the start. Recent news suggests that the City of Los Angeles feels similarly – the city is not interested in buying power from a project that is harmful to wildlife and the desert.

Defenders biologists have spent many hours mapping wildlife habitat data, migration corridors, seeps and springs, and other important natural resource values in the California desert. With all of the important places for conservation excluded, there is still ample already-degraded desert land appropriate for large-scale solar energy development, and that is where we should be directing projects. We have used this information to inform the Desert Renewable Energy Conservation Plan (DRECP) that will establish zones for solar energy development and zones for protection of wildlife and important resources. Our hope is that the DRECP will direct future solar energy projects to much more appropriate locations than the Soda Mountains; and that the bighorn sheep will be able to expand and migrate between mountain islands as they have always done.