When I refer to a strong scientific basis, I'm referring to things like a quantitative basis that we can apply repeatedly across the landscape in defining and monitoring ecosystems, so we can determine the status through time. Monitoring allows us to learn and adapt over time. Without that, we will not be able to monitor exactly what's going on and adapt to the changes.
The other one is very simply applying ecological principles that have been developed around the world in defining parks—size of parks, the complexity of parks—and then finally ecological systems.