Sustainability Series: Hidden Habitat Implications of California’s Dry Weather

ELGL presents a new series focused on natural resources and land use management. Dudek, a California-based environmental firm with 400+ planners, scientists, civil engineers, and contractors, will author the series which is creatively titled the Sustainability Series (until someone comes up with something more clever)!

Dudek assists private and public clients on a broad range of projects that improve communities, infrastructure, and the natural environment. From planning, design, and permitting through construction, they help move projects forward through the complexities of regulatory compliance, budgetary and schedule constraints, and conflicting stakeholder interests.


Hidden Habitat Implications of California’s Dry Weather

By: Mike Sweesy, Principal Landscape Architect and Senior Habitat Restoration Expert

Project owners with pending permitting and habitat mitigation programs need to plan for potential setbacks if California’s extended dry weather continues.

California had its worst drought conditions in 90 years between January and May last year, and the first seasonal snow survey in early January of this year showed the state’s water content at about 20% of average. Dudek cites three potential negative implications if the dry weather extends past April.

  1. Delays to Habitat Mitigation Projects

A seed shortage for native plant species will likely occur that could delay implementing habitat mitigation requirements on construction projects.

Native species flower year-round but spring is when the largest number of native species flower. It’s likely these plants won’t form seeds without greater rainfall. In typical seasons, seeds are collected by experts and then sold for use in mitigation projects. Plant species can still flower in the dry conditions but it would be deceptive. 

Without adequate water resources, viable seeds won’t form even though the plant flowers.

Resource agencies often require as part of mitigation that seeds used in mitigation come from within 5–20 miles of the mitigation site to be consistent with local genetic populations. This limits the source vegetation where seed can be collected. It pays to collect seed during wet rain years, even if your project is years away. Also, many seed collection sites in coastal California are located in the wildland-urban interface (WUI) so the local seed supply would be at risk if there are catastrophic fires brought on by extreme drought.

2. High Risk to Non-irrigated Mitigation Projects

Non-irrigated mitigation projects are challenging in normal rain years; during consecutive dry seasons, it is virtually impossible for them to succeed because seeds won’t germinate. Project owners should anticipate losing a year on their mitigation program, if non-irrigated, and expect to pay for adaptive remedial actions such as hand watering container plants, and/or replanting or reseeding when wet weather returns.
In addition, there is increased risk of plant loss due to browsing by local herbivores such as deer and rabbits. As the quality of surrounding “browse” diminishes due to drought, these species are more likely to impact typically more succulent mitigation sites.

3. Permitting Implications for Biology Surveys

Sensitive and rare plant species may not come up in these dry years, so vegetation surveys may not detect the presence of a rare plant population or the full extent of the population. A drought year can leave open questions about potentially significant constraints on land use such as the presence of a rare or endangered plant or animal species.

“Required focused surveys for some species may not even be possible or only partially possible,” says Brock Ortega, a Dudek senior biologist. “For example, fairy shrimp surveys might be compromised because few to none of the vernal depressions might support standing water for a long enough period to support a shrimp life-cycle. If this occurs during a low-rainfall year, then the wildlife agencies usually question the negative survey results.”

As an example of the dry spell’s domino effect, dormant coastal sage scrub could threaten the California gnatcatcher (Polioptila californica) population. Coastal sage scrub supports the gnatcatchers’ food supply of insects and spiders. Dormant vegetation will reduce the insect population, and the resulting stress will trickle up the food chain. Native vegetation also hides the gnatcatchers’ nests and protects them from rain, dew, and too intense direct sunlight. Drought-stressed vegetation makes the nests more exposed and susceptible to failure.

It’s frustrating that no short-term action can be taken to counter these problems except to monitor the extent of the impact and be prepared to adjust plans when the situation changes. Our awareness of these hidden ramifications allows us to recommend mitigation strategies that inoculate clients and their projects from the climate-driven delays. Such recommendations might seem strange at the time, but these are the years that demonstrate the wisdom of forward thinking.