Succulent plant diversity as natural capital

Societal Impact Statement Drought‐tolerant plants are increasingly recognized as a resource to mitigate the consequences of climate change. Succulent plants use stored water to sustain metabolism during regular droughts; succulence is a highly successful adaptation that has evolved in thousands of species throughout the plant kingdom. Desert (xeromorphic) succulent species are a potentially relevant resource to manage environments and energy supply in the hottest and driest places. However, many species are threatened with extinction or could become invasive outside their natural range. This review highlights research needed to develop desert succulents as a sustainable resource in a carbon economy. Summary Drought and increased temperature of the Earth's surface pose significant social and economic challenges under the anticipated effects of climate change. The presence of a reservoir of water to sustain metabolism under drought conditions is a conceptually simple, but remarkably complex, adaptation in the plant kingdom known broadly as succulence. The trait has arisen repeatedly among flowering plant lineages: thousands of succulent species representing immense taxonomic diversity are found on all continents except the polar regions. The phylogenetic diversity and ecological adaptations of desert‐adapted (xeromorphic) succulent plants could be particularly relevant resources to meet the challenges of environmental change, in applications as varied as bioenergy, urban greening, and high‐value products. However, a more complex picture is emerging in which xeromorphic succulents endemic to arid and semi‐arid regions could be at risk of extinction due to habitat loss and exploitation, while others could become invasive if introduced outside their natural range, thus compounding an existing problem of invasive succulent plant species. This review aims to summarize the state of current knowledge of xeromorphic succulent plants as a resource, draw attention to conservation concerns, and examine the potential for their unique traits to be harnessed in a climate change‐resilient world.