DISCUSSION

We found considerable opportunity for alignment of biodiversity con­servation and solar energy development objectives in the Mojave Des­ert. Assessed at the moderate 3% slope cutoff, over 580,000 ha of lands with lower conservation value yet presumably suitable for solar energy development currently exist across the desert, an amount that could supply over five times the energy needed to meet the projected 2020 California 33% RPS goal. Steering development to areas of lower conservation value could help reduce adverse impacts to desert ecosystems, specifically areas that are more intact and those that contain sensitive resources. Avoiding those areas will likely improve the adaptive capacity of desert species in the face of climate change and provide greater ecological resilience in the future. Prioritizing development in lower conservation value lands reduces the prospect of conflict over ecological impacts that can add cost, delay, and controversy to projects.

One striking finding from this study is the relationship between land ownership, conservation value, and “attractiveness for development.” From a conservation perspective, most of the areas that appear better suit­ed for development are privately held, but they are often comprised of many parcels that would need to be consolidated to achieve a minimum area sufficient to support a project. From a development perspective, that parcelization creates a disincentive, especially if an alternative exists to have a more streamlined process working elsewhere with one land owner, e. g., BLM. Thus, one strategy to enhance protection of the conservation values of the Mojave Desert would be to develop policies that incentiv – ize development on degraded private lands. We note that brownfields and areas formerly in agricultural production, but retired due to salinity, wa­ter limitations, economic considerations, or other contamination problems may present ideal locations for solar development, especially for technolo­gies that use less groundwater than the former land use.

The approach we present can also help direct compensatory mitiga­tion investments. By accounting for the direct impacts of a given set of proposed projects and the distribution of lands with higher conservation value, we illustrate how one can generate a portfolio of candidate areas for compensatory mitigation that meet mitigation obligations while contribut­ing to regional conservation goals. Of course, further field assessment is required to ensure that candidate sites generated from this type of analy­sis are indeed suitable as mitigation. This approach can be generalized to other land uses, geographies, covered resources, and mitigation ratios and actions, and explored as a site-selection problem to optimize various social and ecological goals.

Our analysis of land ownership and conservation value also revealed a conundrum for mitigation. While the higher degradation of private lands provides opportunities to avoid or minimize adverse ecological impacts when siting projects, it also poses problems if compensatory mitigation can only be conducted on private lands. The limited supply of private lands with higher conservation values could in turn limit the amount of energy development for which impacts can be offset. We note, however, that there may be considerable opportunity to use mitigation funds to en­hance the conservation management of existing public lands in the des­ert, through such actions as eradicating invasive species, increasing en­forcement of off-highway vehicle closures, or installing tortoise exclusion fencing along roads. The desert tortoise recovery plan [41], for example, recommends numerous management actions to enhance species viability, many of which go unimplemented due to insufficient funding [42]. We emphasize that any investment of mitigation resources applied to public lands would need to result in enduring conservation outcomes and add to the current level of management activities rather than replace existing resources and agency obligations. One way to track and better ensure that investments result in enduring conservation is to change the designation of lands serving as mitigation from one that allows multiple uses to one that gives primacy to the conservation use. Ensuring additionality of mit­igation-related enhanced management funding would likely involve con­tractual obligations and require special enforcement mechanisms within agency budgeting processes.

We underscore the importance of accounting for cumulative impacts in siting and mitigation decisions, especially in light of the increased stress that climate change will exert on desert ecosystems. The impacts of proj­ects should not only be evaluated comprehensively regarding ecological impacts, but also examined cumulatively in the context of all of the ma­jor stressors in the desert (including but not limited to the other proposed energy projects). Because of the large area potentially impacted by long­term solar energy development (as illustrated in Figure 6), and the lack of related impact studies, a framework is needed in the near term to guide decision-making to help reduce the risk of inadvertently crossing thresh­olds of ecological viability [8]. The approach presented here, essentially an application of the precautionary principle, can provide that initial guid­ance: develop first in the least conflict areas and protect the consensus conservation areas; meanwhile, improve knowledge regarding the areas in between, so that siting and mitigation decisions in the future can be better informed as to their environmental trade-off.

Limitations of this analysis are mostly related to data quality and reso­lution. We underscore that this study cannot substitute for site-level assess­ment, or more detailed assessments of sensitive and rare species’ conser­vation needs (e. g., HCPs [Habitat Conservation Plans], NCCPs [the state of California’s Natural Communities Conservation Plans], endangered and threatened species recovery plans). Moreover, the map of the relative conservation value should not be construed as a development and con­servation blueprint, per se. Randall et al. (2010) caution that because im­portant occurrences, ecological processes or habitats of targets may occur within all of the conservation value categories, even the Highly Converted category, site-level assessment is needed to confirm suitability for devel­opment, and guide project siting, design, and mitigation. The Assessment is best used to provide general guidance to planners and industry seek­ing to assess the relative likelihood of environmental constraints across a broad area, in an attempt to minimize adverse permitting problems. As suitable information becomes available, the approach we present here can be implemented at a finer spatial scale for a portion of the ecoregion.

An additional limitation of our analysis is that it does not explicitly ac­count for some key factors that influence the economic feasibility of proj­ect development. Geographic factors may affect the economic profitability of a site, such as local influences on solar radiation or the costs of ongoing maintenance to minimize damage from airborne sand. One notable factor that was beyond the scope of our study pertains to transmission. Proxim­ity to transmission corridors that have additional capacity is an important consideration in siting new generation facilities. The relationship between transmission and generation will be important to incorporate into future refinements of this analysis utilizing the expertise of the solar industry, es­pecially where new transmission is required to service proposed facilities. Those additional impacts should be incorporated into the overall applica­tion of the mitigation hierarchy.

In sum, we demonstrate how solar energy production goals in the Mo­jave Desert can be met with less adverse effect on biodiversity. The sys­tematic approach presented here for proactively balancing solar energy production with biodiversity protection better accounts for, and so can help reduce, trade-offs. Importantly, it can also provide greater assurances to agencies, developers and conservationists that their respective goals are being met. Integrating this sort of analysis with dynamic information systems for species distributions, ecological condition and conservation investments, can help agencies and stakeholders adaptively apply the mit­igation hierarchy with increasing effectiveness. This example of multi­objective planning can also be expanded and tailored to other technolo­gies and geographies, e. g., wave energy and marine protected areas. We caution, however, that if such planning does not incorporate and accom­modate all major interests and stakeholders, it may lead to displacement of one user by another, and exacerbate rather than resolve conflict. For example, our analysis did not incorporate some significant desert values, such as cultural values, recreational uses, military training, and scenic val­ues. Accounting for this array of interests will be essential for developing the long-term conservation plan for the Mojave.

Numerous conservation and energy development planning efforts are currently underway that will affect the Mojave Desert (e. g., BLM’s Solar Energy Development Programmatic Environmental Impact Statement). The State of California is currently developing an NCCP for the state’s deserts that, like this analysis, will take into account not just those species currently listed but the full array of natural communities of the Califor­nia deserts. We are hopeful that the resulting NCCP will identify areas preferred for development and conservation, and institutionalize effective regulatory mechanisms and market-based incentives to implement that plan. Ideally, those mechanisms will help ensure that siting and mitigation occur in the places most appropriate for effecting desert conservation-re­gardless of the underlying ownership. In the interim, we propose that a precautionary approach like that presented here could guide conservation – compatible renewable energy development in the desert.

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