Two tortoise species native to the American southwest have experienced significant habitat loss from development and are vulnerable to ongoing threats associated with continued development. Mojave desert tortoises Gopherus agassizii are listed as threatened under the US Endangered Species Act, and Sonoran desert tortoises G. morafkai are protected in Arizona (USA) and Mexico. Substantial habitat for both species occurs on multiple-use public lands, where development associated with traditional and renewable energy production, recreation, and other activities is likely to continue. Our goal was to quantify development to inform and evaluate actions implemented to protect and manage desert tortoise habitat. We quantified a landscapelevel index of development across the Mojave and Sonoran desert tortoise ranges using models of potential habitat for each species (152 485 total observations). We used 13 years of Mojave desert tortoise monitoring data (4732 observations) to inform the levels and spatial scales at which tortoises may be affected by development. Most (66−70%) desert tortoise habitat has some development within 1 km. Development levels on desert tortoise habitat are lower inside versus outside areas protected by actions at national, state, and local levels, suggesting that protection efforts may be having the desired effects and providing a needed baseline for future effectiveness evaluations. Of the relatively undeveloped desert tortoise habitat, 43% (74 030 km2) occurs outside of existing protections. These lands are managed by multiple federal, state, and local entities and private landowners, and may provide opportunities for future land acquisition or protection, including as mitigation for energy development on public lands.

中文翻译：

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量化发展以告知美国西南部莫哈韦沙漠和索诺兰沙漠龟栖息地的管理

两种原产于美国西南部的陆龟物种因发展而经历了重大的栖息地丧失，并且容易受到与持续发展相关的持续威胁。莫哈韦沙漠陆龟 Gopherus agassizii 被美国濒危物种法列为受威胁物种，而索诺兰沙漠陆龟 G. morafkai 在亚利桑那州（美国）和墨西哥受到保护。这两个物种的大量栖息地位于多用途公共土地上，与传统和可再生能源生产、娱乐和其他活动相关的开发可能会继续进行。我们的目标是量化发展，以告知和评估为保护和管理沙漠龟栖息地而实施的行动。我们使用每个物种的潜在栖息地模型（总共 152 485 次观察）量化了莫哈韦沙漠和索诺兰沙漠陆龟范围内的景观水平发展指数。我们使用了 13 年的莫哈韦沙漠陆龟监测数据（4732 次观测）来告知陆龟可能受到发展影响的水平和空间尺度。大多数 (66-70%) 沙漠陆龟栖息地在 1 公里范围内有一些发展。与受国家、州和地方各级行动保护的外部区域相比，沙漠陆龟栖息地的开发水平较低，这表明保护工作可能会产生预期效果，并为未来的有效性评估提供所需的基线。在相对未开发的沙漠陆龟栖息地中，43%（74 030 平方公里）发生在现有保护范围之外。