Research by Lundgren, Wallach and Ramp suggests that wild equids are filling the void of extinct megafauna and are contributing to biodiversity. In particular, they have been found to find water in desert areas which are used by many species. There is also evidence that wild horses are doing this in Australia.
“…research didn’t evaluate the impact of donkey-dug wells in arid Australia. But Australia is home to most of the world’s feral donkeys, and it’s likely their wells support wildlife in similar ways.
Across the Kimberley in Western Australia, helicopter pilots regularly saw strings of wells in dry streambeds. However, these all but disappeared as mass shootings since the late 1970s have driven donkeys near local extinction. Only on Kachana Station, where the last of the Kimberley’s feral donkeys are protected, are these wells still to be found.
In Queensland, brumbies (feral horses) have been observed digging wells deeper than their own height to reach groundwater. “https://theconversation.com/feral-desert-donkeys-are-digging-wells-giving-water-to-parched-wildlife-159909