Weil said that the long recovery period is perhaps not surprising. While a species' extinction does not leave an empty niche, it destroys all or part of other niches. For example, it removes opportunities for predators, parasites and other organisms that would normally rely on that species. Extinction also is a lineage termination, which removes a potential ancestor from which other species could evolve. Extinction is a double whammy.
Diversification takes a long time to ramp up.
Such complexity may also be the reason that the size of the extinction is relatively unimportant in determining the time it takes the ecosystem to recover. Extinction totally alters the ecosystem, making recovery a slow process no matter what the scale. Life reaches a new but different plateau. Kirchner notes that their sobering findings don't necessarily imply a stark fate for the Earth. Our future depends on what we choose to do on a national and international level, as a society.