Aim  Climate change poses significant threats to biodiversity, including impacts on species distributions, abundance and ecological interactions. At a landscape scale, these impacts, and biotic responses such as adaptation and migration, will be mediated by spatial heterogeneity in climate and climate change. We examine several aspects of the geography of climate change and their significance for biodiversity conservation. Location  California and Nevada, USA. Methods  Using current climate surfaces (PRISM) and two scenarios of future climate (A1b, 2070–2099, warmer‐drier and warmer‐wetter), we mapped disappearing, declining, expanding and novel climates, and the velocity and direction of climate change in California and Nevada. We also examined fine‐scale spatial heterogeneity in protected areas of the San Francisco Bay Area in relation to reserve size, topographic complexity and distance from the ocean. Results  Under the two climate change scenarios, current climates across most of California and Nevada will shrink greatly in extent, and the climates of the highest peaks will disappear from this region. Expanding and novel climates are projected for the Central Valley. Current temperature isoclines are projected to move up to 4.9 km year−1 in flatter regions, but substantially slower in mountainous areas because of steep local topoclimate gradients. In the San Francisco Bay Area, climate diversity within currently protected areas increases with reserve size and proximity to the ocean (the latter because of strong coastal climate gradients). However, by 2100 of almost 500 protected areas (>100 ha), only eight of the largest are projected to experience temperatures within their currently observed range. Topoclimate variability will further increase the range of conditions experienced and needs to be incorporated in future analyses. Main Conclusions  Spatial heterogeneity in climate, from mesoclimate to topoclimate scales, represents an important spatial buffer in response to climate change, and merits increased attention in conservation planning.

We examined variation in leaf size and specif ic leaf area (SLA) in relation to the distribution of 22 chaparral shrub species on small-scale gradients of as pect and elevation. Potential incident solar radiation (in solation) was estimated from a geographic information system to quantify microclimate affinities of these spe cies across north-and south-facing slopes. At the com munity level, leaf size and SLA both declined with in creasing insolation, based on average trait values for the species found in plots along the gradient. However, leaf size and SLA were not significantly correlated across species, suggesting that these two traits are decoupled and associated with different aspects of performance along this environmental gradient. For individual spe cies, SLA was negatively correlated with species distri butions along the insolation gradient, and was signifi cantly lower in evergreen versus deciduous species. Leaf size exhibited a negative but non-significant trend in re lation to insolation distribution of individual species. At the community level, variance in leaf size increased with increasing insolation. For individual species, there was a greater range of leaf size on south-facing slopes, while there was an absence of small-leaved species on northfacing slopes. These results demonstrate that analyses of plant functional traits along environmental gradients based on community level averages may obscure impor tant aspects of trait variation and distribution among the constituent species.

Thermal environments in a large, topographically diverse serpentine soil—based grassland were quantified and ranked using a computer model of clear sky insolation and shading on different slopes to determine the effects of microclimate on the rates of development of each of the life stages of the butterfly Euphydryas editha bayensis. Larvae developed to pupation earlier on warm slopes than on progressively cooler slopes. Availability of sunlight can be limiting for larvae, which bask indirect sun to raise body temperature. Larvae can disperse >10 m/d, allowing them to transfer between microclimates. Pupae on warmer slopes also developed faster than those on cooler slopes. Microclimate also affects the phenology of host plants of larvae and nectar sources of adults. Larval and pupal development and host—plant phenology determine the phase relationship between adult butterfly flight and host—plant senescence, which in turn determines mortality rates of prediapause larvae. Adult females that eclosed early in the season could have their offspring survive on almost all slopes, survivorship of offspring from adults that eclosed in the middle of the flight season was restricted to cooler slopes in the habitat. Some butterflies eclosed too late for their offspring to survive on any slope. Topographic diversity on several scales is a prime indicator of habitat quality for this butterfly. Areas of high local topographic diversity on a scale of tens of metres appear particularly important for long—term population persistence under variable climatic conditions.

Most conservation planning to date has focused on protecting today's biodiversity with the assumption that it will be tomorrow's biodiversity. However, modern climate change has already resulted in distributional shifts of some species and is projected to result in many more shifts in the coming decades. As species redistribute and biotic communities reorganize, conservation plans based on current patterns of biodiversity may fail to adequately protect species in the future. One approach for addressing this issue is to focus on conserving a range of abiotic conditions in the conservation-planning process. By doing so, it may be possible to conserve an abiotically diverse "stage" upon which evolution will play out and support many actors (biodiversity). We reviewed the fundamental underpinnings of the concept of conserving the abiotic stage, starting with the early observations of von Humboldt, who mapped the concordance of abiotic conditions and vegetation, and progressing to the concept of the ecological niche. We discuss challenges posed by issues of spatial and temporal scale, the role of biotic drivers of species distributions, and latitudinal and topographic variation in relationships between climate and landform. For example, abiotic conditions are not static, but change through time-albeit at different and often relatively slow rates. In some places, biotic interactions play a substantial role in structuring patterns of biodiversity, meaning that patterns of biodiversity may be less tightly linked to the abiotic stage. Furthermore, abiotic drivers of biodiversity can change with latitude and topographic position, meaning that the abiotic stage may need to be defined differently in different places. We conclude that protecting a diversity of abiotic conditions will likely best conserve biodiversity into the future in places where abiotic drivers of species distributions are strong relative to biotic drivers, where the diversity of abiotic settings will be conserved through time, and where connectivity allows for movement among areas providing different abiotic conditions.

Nutrient-poor, serpentinitic soils in the San Francisco Bay area sustain a native grassland that supports many rare species, including the Bay checkerspot butterfly ( Euphydryas editha bayensis ). Nitrogen (N) deposition from air pollution threatens biodiversity in these grasslands