There are cogent ecological and socioeconomic arguments for establishing MPAs with long-term, defined boundaries, although there has to be flexibility for adjusting zones, such as ecological or fishery reserves, within MPAs to maximize effectiveness. Damage to habitats and fish populations from human activities can occur very quickly, but recovery often requires a long period of time. For example, biogenic habitat such as deep-sea corals once damaged by trawling could take many decades to recover. Also, when fish stocks collapse, recovery may be slow, especially for long-lived species that take many years to reach reproductive maturity. If reserves are designed in the context of supporting the surrounding ecosystem they can serve as the ecological equivalent of a trust fund: the fish stocks and habitat within a reserve will provide a long-term investment in the productivity of the ecosystem as a whole.