Equids engineer desert water availability.

The research article investigates the role of megafauna, specifically donkeys and horses, in enhancing water availability in desert regions of North America through the digging of wells. The study found that these equids contribute to water density, access and at times, offered the only source of water. They also increase the richness and activity of vertebrates and provide habitats for riparian trees, thereby possibly increasing the resilience of these areas to human-caused desertification.

Role of Equids in Desert Water Availability

• The researchers focused on the activities of donkeys and horses, known as equids, in the arid regions of North America. These equids were observed to dig wells up to 2 meters deep to reach groundwater.
• This digging activity was reported to enhance the availability of water in the desert, by increasing the density of water features and reducing the distances between waters.
• In certain instances, the water from the wells dug by these feral equids was the only water present in these drylands.

Impact on Biodiversity

• The study found a positive correlation between the well-digging activity of equids and biodiversity in the desert. Specifically, vertebrate richness and activity were higher at the sites of equid wells as compared to other dry sites.
• This means that the presence of these wells dug by equids encourages the proliferation of other vertebrates in the region.

Equid Wells as Nurseries for Riparian Trees

• Further, the research discovered an association between equids’ well-digging and the growth of riparian trees – trees that grow along river banks.
• The wells dug by the equids simulated flood disturbance, conducive for the growth of these trees. As a result, these wells in the desert became nurseries for riparian trees.

Contributions to Ecosystem Resilience

• The study suggests that the activities of equids could contribute to greater resilience of desert ecosystems to human-caused desertification or aridification.
• By enhancing water availability, promoting biodiversity, and supporting the proliferation of riparian trees, these feral or introduced equids seem to play a vital role in maintaining the health and resilience of these arid ecosystems.