Protecting & Restoring Long Island's Peconic Bays

Climate Change

Climate change is profoundly impacting the Peconic Estuary through increasing water temperatures, changes in precipitation patterns, sea level rise, and ocean acidification.

House on stilts on the shore of the Peconic Estuary.


Conservative projections for the Long Island region include air temperature increases ranging from 3°F to 5°F by 2050, along with greater temperature variability, increased seasonality, and higher frequency of extreme temperature events. Ocean temperatures in our region are expected to rise between 4°F and 8°F over the next century.


While increases in annual precipitation are expected to be relatively minor, the amount of precipitation falling as part of an “extreme” precipitation event and the frequency of such events is expected to increase, as is the frequency of drought.

Sea Level Rise

Globally sea levels are rising in part due to expansion of oceanic waters as average temperatures increase and in part due to increased amounts of available freshwater from melting glaciers and land-based ice. Locally, sea level is expected to increase from 2 to 5 inches by the 2020s, and 7 to 12 inches by the 2050s. Rising seas are likely to causes stresses on habitat, human populations and natural resources. As sea level increases, we may expect an increase in demand for hardened shorelines. An environmentally beneficial alternative to hardening shorelines is construction of living shorelines which may also have positive impacts on habitat.

Ocean Acidification

As an increasing amount of carbon dioxide (CO2) accumulates in the atmosphere, there is a similar increase in the amount of CO2 that is transmitted to the oceans. When CO2 dissolves in salt water a series of chemical reactions take place that result in a decrease in the overall pH of the water, meaning that the water becomes more acidic. The process is called ocean acidification. The ocean pH is now lower than any time in the last 420,000 years and if current trends continue, the average pH of the oceans could drop by as much as 0.5 pH units relative to preindustrial levels.

Summary of Climate Factors for the Peconic Estuary Region



What are the Impacts?

Water Quality: Changes in precipitation patterns, in particular the projected increases in total precipitation and extreme rain events, will likely lead to increased land based runoff of nutrients, herbicides, and pesticides and may also lead to increased atmospheric deposition. Additionally increases in sea level will likely result in regular inundation of septic systems in coastal communities, either through regular tide cycles or elevation of groundwater level. This will lead to increases in the amount of nitrogen and pathogens transmitted directly to estuarine waters.

Impacts on Harmful Algal Blooms: The many impacts of climate change are likely to directly influence the occurrences, types, abundance, distribution and duration of harmful algal blooms in Peconic Estuary waters. Increased nutrient loading to the waters of the Peconic Estuary will provide more food for harmful algal blooms. Additionally, since harmful algal booms generally occur during the warm summer season, increasing water temperatures may result in earlier and more frequent blooms. Warming temperatures could also prevent mixing of the water, and allow the algae to grow thicker and faster.

Erosion behind a bulkhead on the shore.

Impacts on Marine Habitats: Climate change is linked to the loss of eelgrass, wetlands, and other marine habitats, which provide an important feeding and nursery habitat for recreational and commercial fisheries.

  • Research suggests that rising water temperatures and reduced water clarity are contributing to the loss of eelgrass beds.
  • Wetlands can migrate inshore gradually with rising water levels. However, the rate at which the sea-level is rising is making it difficult for wetlands to migrate inshore fast enough. In many cases around the Peconic Estuary low marsh plants are not able to hold their ground and high marsh plants are becoming more dominant in wetlands. In areas with significant coastal development and shoreline hardening, coastal habitats will be prevented from migrating landwards as sea level rises.

Impacts on Fish Populations: Rising average water temperature has the potential to alter the species composition throughout the Peconic Estuary. Fish surveys show that since 1987 the average number of warm-adapted species has increased in the Estuary while the average number of cold-adapted species has decreased. Since the estuary consists of a diverse community of native marine species which rely on specific food resources and habitats to survive, it is unclear exactly how a range shift of immigrating warm water tolerant fish species to the estuary and emigrating cold water fish species from the estuary will alter ecosystem dynamics for native community members.

Impacts on Shellfish Populations: Increasingly acidic oceanic waters limits the ability of calcifying organisms, like shellfish, to build their shells or skeletons.

Impacts on Groundwater: Groundwater supplies are being threatened as sea-level rises. The saltwater interface will increase in elevation and will result in the reduction of thickness of the freshwater aquifer system. This is a threat to our drinking water supply and our freshwater fed habitats.

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