“The natural world is the larger sacred community to which we belong. To be alienated from this community is to become destitute in all that makes us human. To damage this community is to diminish our own existence.” Thomas Berry

Bacteria, plants, fungi, animals, along with we humans, are all connected. None can live isolated from the others. Many plants depend on pollinators (some are wind pollinated). All are linked with soil fungi and bacteria for more efficient transmission of soil nutrients and minerals into the plants’ roots. Animals are linked to the other groups for nourishment, digestion, and oxygen. These interdependent relationships can be referred to as natural communities. As essential as these communities are for life on earth, to a large extent much of science and natural history has been focused on individual species. Naming species, placing them within orders, families, genera, and then giving them a unique species epithet has been the focus. In giving them names, we attribute them with importance. They are unique and potentially deserving of protection under state or federal laws. This species focus continues with modern digital approaches to recording nature, such as iNaturalist or eBird. This species-focus is useful for understanding patterns of biodiversity across our planet. However, by not incorporating the idea that the community to which those species belong deserves a similar level of importance we may be putting the communities which these species depend on at risk.

Frederic Edward Clements and Edith Gertrude Schwartz teamed up to identify the character of plant communities in the early 1900s. They visualized communities as a group of associated species whose composition was repeated across landscapes where similar climates, geology, and topography occur. They described these communities as changing over time until they became a stable climax community. Think of a site that has been burned by a wildfire. Initially, immediately following the fire, a group of plant species appear, typically short-lived annual wildflowers. These “fire-followers” would then be replaced with longer lived shrubs in a process referred to as succession. Finally, the shrubs would be succeeded by very long-lived trees, the climax community. Each community represents a successional stage that was necessary to create the conditions required for the next community to become established. This view of nature was called Clementsian. European naturalists argued that communities in nature had sharp boundaries. There was a marsh, then a meadow, and then a forest in succession, each with clear edges. You were either in one or the other.

As much as that Clementsian paradigm seemed to make sense, there were critics. Henry Allan Gleason and Sir Arthur George Tansley were contemporaries of Clements and Schwartz but saw nature not as an orderly succession of communities with sharp boundaries, but as individual species that occurred together, or not, only when particular habitat needs that they shared were present. Sun-loving, arid-tolerant species tended to occur together, and shade and moisture tolerant species would also co-occur. This Gleasonian view saw communities as associations of species with similar ecological needs, not as a succession of species that was necessary to pave the way for the next community. Gleason and Tansley went into those post-disturbance communities and found seedling forest trees hidden among the annual wildflowers. Gleasonian naturalists saw communities not with sharp boundaries, unless there were sharp boundaries in the underlying ecological conditions, but as individual species occurring along a gradient with varying levels of overlapping habitat needs. Ultimately the Gleasonian paradigm was adopted by the majority of naturalists and ecologists, but rather than providing clarity and simplicity to the idea of what is a natural community, it underlined the actual complexity that such species associations entail.

Within the Colorado Desert, creosote bush scrub is the dominant low elevation community. Still, creosote can co-occur with brittlebush, with burro bush, or with some combination of the two. When is it a different community? Or does it matter? Plant ecologists have recently opted to eschew the use of “community” as an identifying category, instead using “plant alliances and associations.” In the above example, the “community” would be classified as the creosote bush alliance, with a brittlebush association, or a burro bush association, or a brittlebush-burro bush association. The idea being that the alliance reflects the dominant perennial plant species, either numerically, structurally, or ecologically dominant. The association reflects the next most dominant perennial species. 

When we applied this alliance-association scheme to active desert sand dunes we encountered a different set of problems. On active sand dunes almost by definition there are no dominant perennial plants. If there were dominant perennial vegetation present, the dunes would not be active. So, what should we call it? We consulted the state-level experts but got little help. The experts had not worked much in deserts and certainly not on sand dunes; they were used to working in densely vegetated landscapes, not the sparse character of deserts, and especially not sand dunes. Yet sand dunes are an iconic desert community, often populated with animals and annual plants found nowhere else on earth. If the alliance-association classification scheme was going to be adopted, and if it was going to be used to inform conservation strategies and priorities, then sand dunes need to work in that scheme. Ultimately, we received an ok to use annual plants, such as dune primrose and the Coachella Valley milkvetch as alliances, and then use other species, like sand verbena, as associations.

Whether the alliance-association classification will fully replace “communities,” or whether a new scheme might someday be developed, only time will tell. In any case, a shift from only using species to identify conservation priorities is needed. A species-based approach can lend itself to “postage stamp” conservation solutions, whereas whenever possible whole functioning ecosystems should be the targets. A more comprehensive conservation scheme should incorporate species, some sort of vegetation alliance-association matrix, ecological processes (such as wind and flooding moving sand) that maintain those species and alliances, and aquifers quenching the thirsts of mesquite thickets and palm oases, and below ground microbial processes that sequester carbon and ensure nutrients reach plant roots. Over much of the planet, such a comprehensive approach may not be possible. People have already altered nature too much and so postage stamp protection is all that is left. However, in deserts incorporating all the species connections and needs is still possible.

Nullius in verba

Go outside, tip your hat to a chuckwalla (and a cactus), think like a mountain, and be safe.