Basis: The value of 43 was based on an authoritative review of historical losses of wetlands in the three Bay states since colonial times and a U.S. Fish & Wildlife study on the annual rate of losses. Assuming that the rate of loss within the watershed was roughly comparable to the statewide losses, these two studies would indicate that the watershed has lost 57 percent of its wetlands since colonial times.
Observations: Wetland restoration efforts have accelerated, but the protection of existing wetlands remains precarious. Recent court rulings and proposed changes in legal and regulatory programs that govern existing regulations threaten existing wetlands. Although the rate of loss of existing wetlands may have slowed somewhat from the 1980s, proposals for large projects that would destroy hundreds of acres of wetlands at a time are being considered.
Forested Buffers 53
Basis: The value of 53 is based on a Chesapeake Bay Program fact sheet, “A Snapshot of the Chesapeake Bay: How’s it Doing?” which states that 53 percent of the basin’s 110,000 miles of streams and shorelines are buffered by riparian forests.
Observations: Efforts to restore forested buffers have expanded, and the acreage of restored buffers is increasing. At the same time, the inadequate enforcement of existing laws is resulting in losses of existing buffers. It is not yet clear whether restoration efforts can succeed without more attention to preserving existing buffers.
Underwater Grasses 12
Basis: The value of 12 represents the 12 percent, or 69,000 acres, of the widely held estimated historical range of 600,000 acres that is currently covered by submerged aquatic vegetation, or SAV.
Observations: SAV Baywide has increased in the last two years, but Tangier Sound has lost 50 percent of its beds since 1992. Although underwater grasses have increased substantially from the historic low levels of the early ’80s, the Bay has not regained the high set in1993. SAV restoration depends directly on reducing nutrients and sediments from all sources. In addition, increased attention needs to be paid to activities that damage grass beds, such as hydraulic dredging.
Dissolved Oxygen 15
Basis: The value of 15 reflects the severely degraded state of the Bay with respect to dissolved oxygen. Studies by Johns Hopkins University researcher Dr. Grace Bush indicate that anoxia — total deprivation of oxygen — was rare to absent before colonial settlers cleared forests and increased the flow of sediment into the Bay. The levels of anoxia and hypoxia — extremely low levels of oxygen — we see today reflect both nutrient inputs and consequences of river flows that were probably changed forever after land in the watershed was cleared.
Observations: Average dissolved oxygen levels are severely degraded as the result of continued nutrient inputs, and there is no evidence of improvement in recent years. Improved levels are essential to healthy habitat for fish and shellfish and will depend on the reduction of nutrients from all sources.
Water Clarity 15
Basis: The value of 15 indicates a severely degraded Bay in this component. Recognizing that the Bay was never as clear as a mountain lake, it is still apparent that the water today is far murkier than the water of 300 years ago. Reliable reports of widespread underwater grasses that grew in 9 feet of water only a century ago are one indication of deterioration.
Observations: Water clarity is an indicator of nutrient and sediment loadings to the Bay. Excess nitrogen and phosphorus result in unbalanced algae growth that clouds the water. Nutrient reduction is critical to increase water clarity, which has shown no improving trend in recent years. Although erosion and sediment control programs exist, they are not always well-enforced. In addition, losses in the Bay’s natural filters — forested buffers and wetlands — have reduced its ability to filter nutrients and reduce erosion. On a positive note, underwater grasses in some areas grow more than 10 feet deep, suggesting that water clarity restoration is possible.
Basis: The value of 30 indicates that the Bay is deeply degraded. Among all the threats to the Bay, toxic chemicals are the most difficult to measure. Very little is known about their effects, including what effects occur at low levels. Some seemingly harmless chemicals are deadly when mixed together. Others, such as PCBs, dioxins and DDT do damage in extremely small doses. Many chemicals accumulate over time until they, too, do a great deal of damage.
Observations: Regulatory and monitoring systems remain insufficient and the approach of using fewer toxic materials has not been widely adopted. On a positive note, the tonnage of reportable industrial discharges of toxic materials from some industries has declined in the last 15 years.
Phosphorus & Nitrogen 15 Apiece
Basis: The value of 15 is based on estimates that nutrient loadings to the Bay are seven times what they were in pre-colonial times. Fifteen represents the inverse of seven times the loading, or one seventh. While nitrogen and phosphorus occur naturally, man has introduced levels so artificially high that the Bay cannot sustain them.
Observations: By 1989, phosphate in detergents were banned in Maryland, Virginia, Pennsylvania and the District of Columbia, which dramatically reduced the level of phosphates in sewage discharges. Past fertilizer use and the agricultural application of manure has caused a saturation of phosphorus in soils in many areas. Nitrogen continues to reach the Bay from a variety of sources, including air pollution, sewage treatment plants and agriculture. New nutrient management laws in Pennsylvania and Maryland have yet to reduce levels, while legislation in Virginia is still under consideration.
Basis: The value of 50 is based on the judgment that the blue crab population is far below its pre-exploitation level for two reasons: extremely heavy fishing and extremely reduced levels of the underwater grass habitat critical to the species’ life cycle.
Observations: Only the high inherent resilience of the Bay’s blue crab population prevents a lower number in view of the historically high level of fishing effort now targeting this species after the decline of the Bay’s other commercial fisheries. The excessive level of effort may reduce reproduction levels, as smaller crabs do not reproduce as abundantly as older, larger crabs. Widely varying abundance from season to season and a smaller average crab size reduce the fishery’s value.
Basis: The value of 70 is based on three grounds. First, there are not yet enough large, old fish to produce a fully healthy age distribution. Second, there is concern about the health of the individual fish. (A persistent disease afflicts many of the fish.) Third, there is concern that their forage base, primarily menhaden, is reduced in numbers. Meanwhile, rockfish (striped bass) numbers and spawning stock biomass are at the highest levels since relatively good records started being kept in the 1960s.
Observations: The striped bass population has grown from near collapse in the mid-1980s as the result of cooperative, coastwide controls on harvest. More old, large fish are needed in the population to maximize spawning potential, and continued vigilance is needed to ensure that rockfish are never overfished again.
Basis: A value of 1 represents an oyster population that is believed to be less than 1 percent of its abundance in John Smith’s time. Although there is no definite way to estimate the oyster population either in pre-colonial times or today, it has been estimated that oyster biomass in the late 1980s was only 1 percent of what it was before the period of heavy oyster harvest in the late 1800s.
Observations: Oysters continue to be held to a historic low because of disease pressure, irregular reproduction and lack of habitat. Efforts to restore oyster reefs in Maryland and Virginia have shown promising results, and citizen participation in oyster restoration represents an encouraging avenue to bring back the reefs and raise awareness about the value of oysters to the Bay system.
Basis: The value of 2 indicates a population that is almost, but not quite, as depleted as oysters. As an example, the current shad population in the upper Bay is only 3 percent of the restoration target for the Susquehanna, let alone pre-exploitation levels.
Observations: Encouraging, modest improvements in the upper Bay contrast with historic lows in most other areas. Increased interest in restoration — fish passages on the Susquehanna and James rivers — and controls on the ocean fishery give cause for guarded optimism.