Succulent plant diversity as natural capital

Abstract

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.

Plant Power: Opportunities and challenges for meeting sustainable energy needs from the plant and fungal kingdoms

“…Agave (Asparagaceae) and Opuntia (Cactaceae) species can operate at near‐maximum productivity with low water requirements (Borland et al, 2011; Borland, Griffiths, Hartwell, & Smith, 2009) and exhibit lower greenhouse gas emissions and nitrogen leaching than maize (Davis et al, 2012). Opuntia ficus‐indica and Euphorbia tirucalli (Euphorbiaceae) have also been considered potential bioenergy crops and been determined to produce promising yields with low rainfall (Mason et al, 2015) but require careful consideration of the potentially negative ecological impact of introducing invasive species outside their natural range (Grace, 2019). In a global scale GIS‐based productivity model, simulations for the year 2070 on low‐grade land suggested that Opuntia ficus‐indica alone has the capacity to meet extreme bioenergy scenarios (>600EJ yr −1 ) and is highly resilient.…”

“…However, this approach has limitations when the aim is to identify candidate species that may be morphologically dissimilar to relatives known to possess a trait of interest (e.g., domesticated crops and their wild relatives), if the trait has not been systematically characterized in a plant group, and if highly novel candidate species are sought. In those cases, candidate species can be predictively identified from the clades in the tree of life in which that trait is most likely to occur (Ernst et al., 2016; Grace, 2019; Rønsted, Savolainen, Mølgaard, & Jäger, 2008; Zhu et al, 2011). Machine learning analysis, recently successful in the search of new antibiotics (Stokes et al, 2020), could help to separate the search for candidate species from their classification or tree of life altogether, facilitated by curated trait datasets (Kattge et al, 2020).…”

Dynamics of intracellular mannan and cell wall folding in the drought responses of succulent Aloe species

“…In desert environments, plants must be able to cope with all three factors (Moore, Vicré‐Gibouin, Farrant, & Driouich, ). The ability to store and use water in a regulated manner is a remarkable and crucial adaptation in the ecological success of succulent plants (Grace, ), which are estimated to include ca . 12,000 species in diverse lineages of the angiosperm tree of life (Moore et al, ; Nyffeler & Eggli, ).…”

An Aridamerican model for agriculture in a hotter, water scarce world

“…Today, desert plants, especially CAM succulents, are receiving renewed interest as resilient crops and natural capital under climate change (Davis et al., 2019; Grace, 2019; Owen, Fahey, & Griffiths, 2016; Stewart, 2015). Compared to conventional C 3 and C 4 crops, CAM plants require tenfold less water per unit dry biomass produced (Mason et al., 2015).…”