The Benefits of Open Space:  Chapter 3

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Open space is not merely an amenity, a frill among other necessities on the map of a region, a watershed, or a community. Rather it is the matrix where most of the creatures in that region or community live, and it affects and controls and is affected by everything else that is there. In rural communities, this is so obvious that it needs no elaboration. But in developed communities, it is frequently forgotten.

Open space, and especially natural open space (forest, wetlands), is the guarantor of biodiversity, of the continuance on the planet of natural communities of species, of fertility to feed all levels of the food chain including people, and of clean air and water essential to the biological health of all species, including homo sapiens (who frequently do not live up to their name). As natural open space is maintained, so will species richness, habitat diversity, and the health of all species be proportionally maintained. In short, the conservation of species, the protection of biodiversity, the maintenance of clean air, clean water and health is partly and significantly a function of habitat size, that is, amount of open space.

A variety of habitats (forest, wetlands, grassland) provides food, shelter, and space for the planet's many species to reproduce. Many of these exist in complex relationships sometimes referred to as the web of life. Even subtle changes (like a relatively small reduction in forest size) can cause a ripple effect through the food chain or in adjacent habitats, and can starkly illustrate the benefits of open space after it is gone. For example, only a 12-percent loss of forest cover in a watershed will begin to show an impact on the invertebrate life of a stream, while a 33-percent loss of cover will exhibit major impacts (Klein 1979). Tom Gorton's Turning the Tide (an account of watershed conditions in the Chesapeake region) is instructive on this theme.

Filtration of pollutants is a major ecological benefit of forested open space. A forested stream corridor helps to protect the subterranean ecosystem of a stream or river as well as the surface water quality. Research by J. V. Ward and others in the late 1980s shows large numbers of stonefly larvae, amphipods and archiannelids in the zone of transition between the riverbed and the groundwater, even up to 2 miles from the river channel! This portion of a riverine food chain is the first to be affected by pollution from runoff. Unfortunately, a great deal of wisdom is purchased at the price of error. It is cheaper and more effective to maintain habitat, health and water quality by conserving open space than it is to protect it by mechanical or non-natural means. The Cahill Stormwater Report showed this dramatically for water quality. State of the art, best management practices for stormwater control still allow 30 to 40 percent of the pollutants to get through the system (Cahill Associates, 1989). So water quality maintenance is a major benefit of vegetated open space.

Wetlands are crucial not only for maintaining many plants and animals; in New Jersey they are home to about one third of our endangered and threatened species. At the same time, they provide free flood control, free filtration, sediment control, and lots of food! Fully two thirds of our marine fishes require wetlands in some phase of their reproductive cycle. Salt marsh habitats are among the most productive in the world, one acre of salt marsh being equal in biomass to 10 acres of farmland.

Our fresh and saltwater wetlands are invaluable for buffering and controlling the effects of stormwater, by holding the water, slowing it down, and releasing it slowly. The stormwater periodically is necessary to recharge the wetlands; witness what happens in your favorite marsh when there is a drought! Water storage is essential for wildlife dependent on wetlands for breeding success. When impervious cover (pavements, roofs, malls, etc.) in a watershed becomes too high a percentage of the total area, these natural functions of wetlands don't operate as well. If we can conceive of wetlands as giant sponges, we can easily understand that the capacity of a wetland to perform its functions can be impaired by too frequent swamping, instead of periodic swamping. It doesn't take as long as it used to for a flood to develop.

Likewise our forests perform many functions that are not separate in the real world, giving us clean air, clean water, and a diverse array of habitat niches for many species. The forested lands around reservoirs are a hedge against nonpoint source pollution (NPS), something we forget, living as we do in the age of end-of-pipe technology. The same forested watershed that cleanses the downstream water supply also purifies the air, and hosts many mammals and migratory birds. This is especially true in our deciduous forests of mixed oak, and sugar maple/mixed hardwoods, the most botanically diverse forests and the ones with the most animal species (Kane et. al., 1992). These forests with their layered structure (Kricher and Morrison, 1988) provide niches for birds on the forest floor (Ovenbird), in the shrub layer (Wood Thrush), and in the canopy or overstory (Scarlet Tanager). The larger the contiguous forest area, the greater the density of individual animals and birds and the greater the species richness (diversity of species). The number of animals and the number of species are partly a product of forest structure and partly of habitat size.

In fact without a large core or forest interior, certain species drop out of a forest, especially if the forest is fragmented or isolated. Ovenbird has been known to drop out of a tract even at 4000 acres! Isolation of a forest patch reduces the ability of forest species to recruit new breeders, and fragmentation (corridors, power lines, etc.) permits access of cowbirds, grackles, jays, cats and other suburban predators to the forest interior where they would normally not penetrate (Dunne et. al., 1989). A recent study in the Northeast showed how isolation of forest patches reduced density and species richness of neotropical forest birds at six sites following declines in regional forest abundance (Askins and Philbrick, 1987). Loss of forest through development and fragmentation is one cause of a decrease in migratory birds in the hemisphere (Terborgh, 1989) and in New Jersey (Dunne et. al., 1989). Even some of our common and abundant birds (Red-eyed Vireo, Wood Thrush, Eastern Wood-pewee, Ovenbird) are showing declines in New Jersey (Serrao 1985; Leck 1982; Dunne et. al. 1989), and a number of neotropical forest migrants are showing declines over 50 years in the Northeast (Hill and Hagan 1991). A principal benefit of open space is clearly the maintenance of biodiversity.

Even small forest patches, while not large enough to contain large numbers of resident animals or a diversity of interior forest species, still make an important habitat contribution to the migratory birds of our hemisphere. Patches of woods located on streams, rivers, and ridges are heavily used by migrant birds as stopovers for foraging and resting during long flights to the tropics (Dunne et. al., 1989). One outstanding example of this phenomenon was reported in a study of habitat on the streams feeding the Arthur Kill (Kane et. al., 1991). Some 20 species of warblers totaling 100+ individuals were found in one small block-long forested tract on the Elizabeth River in May! New Jersey is replete with other examples: Hudson County Park in Bayonne; Losen Slote in Little Ferry; Tiffany Woods at the edge of Trenton.

Other categories of open space with ecological benefits also should be mentioned. Grassland has been called the most endangered habitat in the world, because of such factors as development and desertification. Certainly in the Northeast, the grassland community of species is suffering a region-wide decline (Vickery et. al., 1995) and requires management if this community is to be preserved. This situation highlights an important principle. Grasslands, pasture, and some croplands provide food both for animals and humans. Farmland and airports, now virtually the only grasslands in New Jersey, support numerous raptors, waterfowl, mammals and a whole group of endangered, threatened and declining species including Upland Sandpiper, the storied Bobolink, and Horned Lark, among others. Mountaintops may support a high percentage of rare species, especially plants. Lakes and bays support a variety of crustaceans, fish, water birds, and mammals.

Ecological benefits of open space are inseparable from social and economic benefits. Healthy aquatic food chains are indispensable for economies such as the recreation, fishing, and tourist industries. The biological benefits of open space also are directly related to human health. About 25 percent of the compounds used in the pharmaceutical industry are found in nature. That number will rise as more research is done on the complex properties of plants and animals. At this point in human history, only five percent of known plants have been screened for medicinal value. Rosy periwinkle was the first plant used in cancer treatment. Recently it was discovered that taxol, from the Pacific Yew in the Pacific Northwest ancient forests, combats breast cancer. Blood from the king crab is used in the diagnosis and treatment of meningitis. Research on the diet of the Hermit Thrush, insects eaten and insects rejected by the bird, led to the discovery of new compounds that influence the heart rate, either slowing it or increasing it, with a possible application for the treatment of heart disease. A species of wild corn was used to stop the spread of a fungus that wiped out 15 percent of the U.S. corn crop in the 1970s. Open space is the repository of all these biological benefits: "There are more things in heaven and on earth than are dreamt of in your philosophy, Horatio."

Humans are sometimes thought of as being over, against, or above the natural world and not part of it. This misperception is a consequence of our having been isolated and insulated from the open spaces that surround us by development, television, malls, consumerism and a host of causes that can cause us to miss very fundamental points about open space-- that it provides our food, our water, our clean air and our very health. At New Jersey Audubon, we hear school children say, in answer to the question "where does water come from?": "the tap." "And where does food come from? " Answer: "the supermarket." It will be a mistake if we forget our connections to the earth. Without open space, our life is diminished. We will never be exempt from the ecological/biological benefits of open space!

References

Askins, R.A. and M. J. Philbrick. 1987. Effect of changes in regional forest abundance on the decline and recovery of a forest bird community. Wilson Bulletin 99:7-21.

Cahill Associates. 1989. Stormwater management in the New Jersey Coastal Zone. Division of Coastal Resources, NJDEP. Trenton, NJ.

Dunne, P., R. Kane, and P. Kerlinger. 1989. New Jersey at the Crossroads of Migration. New Jersey Audubon Society. Franklin Lakes, NJ.

Hill, N.P. and J. M. Hagan, III. Population trends of some Northeastern North American land birds: a half-century of data. Wilson Bulletin 103:165-182.

Kane, P., K. Anderson and D. Rosselet. 1992. Bridges to the Natural World. New Jersey Audubon Society. Franklin Lakes, NJ.

Kane, R., P. Kerlinger and R. Radis. 1991. Birds of the Arthur Kill tributaries, 1990. Records of New Jersey Birds 17:22-33

Klein, R. 1979. Urbanization and stream quality impairment. Water Resources Bulletin 15(4):948.

Kricher, J. and G. Morrison. 1988. Ecology of Eastern Forests. New York.

Leck, C.F. 1982. Declines in some forest birds over 20 years. Records of New Jersey Birds 8:5.

Serrao, J. 1985. Decline of forest songbirds. Records of New Jersey Birds 11:5-9

Terborgh, J. 1989. Where have all the birds gone? Princeton, NJ.

Vickery, Peter D. et. al. 1995. Grassland Birds: An Overview of Threats and Recommended Management Strategies. 1995 Partners in Flight Conference Proceedings (in press).

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