As stated previously, biological diversity, or biodiversity, is the richness of species, both animal and plant, that occupy a given ecosystem. To know what is possible we need to be aware of the theoretical boundaries to species diversity that have been established by scientists. Much of the science that reveals the extent of local biodiversity comes from studying islands.
A few key principals of island biogeography are important to consider understanding the level of biodiversity possible for New York, our „City of Islands‟. The degree of biological diversity is limited by the size of an island — the larger the island, the more species diversity is possible. All things being equal, and with some species always being lost and new species being recruited, a dynamic equilibrium is obtained in which the overall number of species is constant for a given island of a given size.
By the 1970s the world was awakening to the dramatic loss of habitat. These losses have turned vast tracts of ecosystems into small isolated islands of vegetation. It wasn’t very long before the theories of island biogeography were seen to be of practical use in designing and setting aside bio reserves. Questions were being raised as to the optimal size for a reserve to sustainably maintain its biodiversity prior to fragmentation and isolation.
There are parallels to the bio reserve questions that are relevant to the management and sustainability of urban ecosystems. New York City ecosystems have become severely fragmented, reduced in size and biologically isolated by the development of the city.
The number of species that can be contained in most of our parks is severely limited, and we cannot increase the number of species and hence the biodiversity of our ecosystems simply by cramming more species into New York City’s parkland, even if those species once occurred there. Many of the ecosystems within the 5 boroughs, with good management, can move towards a new, lower dynamic equilibrium reflective of their present reduced size and isolation.