Good article. I read that something similar is happening in Africa with the diminishing numbers of wild Sulcatas. They travel all over eating plants and seeds and then "depositing" those seeds elsewhere. This helps to spread plants of different species all over, sort of like bees pollinating flowers to different areas. With their decline so too has come the decline of some plant species. They also provide borrows to a number of other animals by digging them and then moving on and digging more. I will have to find that article.
I find it amazing how well crafted ecosystems are and we as humans usually have no clue the role everything plays. I spend a lot of time at work talking about the usefulness of native ants. Large tortoises fall into the charismatic megafauna category, and most people understand they are an important herbivore in their ecosystem, but not the subtlety of the role.