The edges in this case are the narrow zones of overlap between two differing ecosystems. Species that are well adapted to the ecotone can take advantage of the resources of both adjacent systems as well as the flows of organisms, energy and materials across the edge.
Birds living along the fringes of forests or the edge of the sea are good examples.
You can elaborate the idea from your own experience. The point here is that academics are well adapted for survival and success in their disciplines, but are uneasy when making excursions outside their normal habitats and sources of sustenance. Mathematicians are accustomed to being given priority status, followed by physicists, and so forth. To the practitioner in the physical, earth or life sciences, the edge of mathematics has often seemed like a barrier rather than a transition. Standards are a vital goal, not a defining condition.