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Protecting Habitat in a Changing Climate

By Michael Johnson, Greater Atlantic Region, Habitat Conservation Division

Certain habitats are essential for the survival of many marine species. For example, cod and lobster thrive in cold water, and seagrass beds provide important shelter and sources of food for young summer flounder and other juvenile fish.

NOAA Fisheries Habitat Conservation Division protects the habitats of fish and invertebrates, nationwide, for hundreds of species and their different life stages. We work with fishermen, partner and tribal organizations, and state and federal agencies to ensure that the impacts of human activities on fish habitats are avoided, minimized, or mitigated in some manner. Through this federal consultation process, we provide advice to state and federal agencies, such as recommending that sensitive life stages and areas are avoided, work plans and methods be modified, and programs be established that monitor the effects of these projects on sensitive habitats.

When you add in the complexities of climate change, protecting fish habitats becomes trickier. We expect climate change to exacerbate the impacts of human activities, such as poorly planned land-use practices, pollution, and dredging and filling of wetlands. What information do we need to protect coastal and marine habitats in a changing climate, and how can we apply it?

Sea anemone off Gloucester. Credit: NOAA/Mike Johnson

Rapid Changes in Our Region

Climate change is a global problem, but some conditions are changing more quickly along the northeastern U.S. coast than other parts of the world. For example, the average sea surface temperature in the Northeast Shelf ecosystem has increased by about 1.3°C (2.3°F) since 1854, with about half of this change occurring in the last few decades. Sea surface temperatures are projected to increase by 2 to 4°C (3.6 to 7.2°F) by 2100. Sea levels are also rising more quickly than the global average along some sections of the coastline in our region. Between 1950 and 2009, sea levels rose three to four times more than the global average along a “hotspot” of about 1,000 kilometers (621 miles) from Cape Hatteras to Cape Cod. This  rise in sea level is due to a combination of water volume expanding as the oceans warm (thermal expansion), melting of glaciers and ice sheets, changes to Atlantic Ocean circulation, and land subsidence. Some researchers estimate that sea levels along the northeastern U.S. coast could rise 25 percent more than the global average.

Fish Are on the Move

As ocean waters warm, fish are moving. Fishermen used to catch red hake, for example, off the coasts of New Jersey and New York in the 1970s. Now, fishermen find them more often in the Gulf of Maine.

Red hake distribution (shown by red, yellow, and green) has changed dramatically in the last 30 years (source: Nye et al. 2009)

Red hake are in good company; a study published in 2013 looked at more than 350 species of fish and found that the distributions of large numbers of marine species, such as lobsters, winter flounder, silver hake, and black seas bass have also shifted north. These shifts make managing fisheries a challenge. Some fish may increase in some areas and disappear in others, affecting the ability of fishermen to harvest them. Tracking fish populations is an increasingly important tool for habitat conservation staff and fishery managers.

NOAA Fisheries, with Rutgers University, has developed the OceanAdapt website, a tool for fishermen and fishery managers to track changes in fish species ranges.

Tip of the Iceberg

The movement of fish is the tip of the iceberg—the visible result of many other changes that are harder to see and map. The warming water changes the distribution of important nursery and forage habitat like seagrasses, and can cause hypoxic zones (low oxygen zones) in places like Chesapeake Bay to grow, which can result in large-scale fish die-offs.

Tidal wetlands, which buffer coastal communities from the effects of flooding, erosion, and storm surges, are also vulnerable to the effects of climate change. Sea level rise could cover 17 to 43 percent of our nation’s tidal marshes, which offer food and protection to young fish. Rising sea levels also drive people to put up concrete sea walls to protect property—eliminating the possibility of the tidal wetlands migrating inland, so they just disappear.

In addition, invasive species, like lionfish, can also take advantage of changing conditions, and out-compete the native species; new diseases can flourish; and toxic algal blooms can kill off fish and other marine animals, and close down fisheries.

We’re Going to Need a Bigger Toolbox

With so many changes and interactions, evaluating how climate change may affect fish or fish habitats is no easy task. In some areas, sea level rise and the disappearance of wetlands might have the greatest impact on fish habitat; in others, warming water may change the locations of predator and prey species causing changes up the food chain. We continue to research and develop new tools to identify habitats and species that may be vulnerable to climate change. For example, this year we are developing guidance and tools to assist federal and state agencies in minimizing the impacts of their projects on habitats, while also adapting to the effects of climate change. These new tools will provide projections of how habitats may be affected based on expected responses to temperature, oxygen, salinity, acidity, and other factors. Even with these tools, we cannot always be certain how species and habitats will respond to climate change.

As we go through this period of rapid change, we will continue to study the effects and adjust the tools in our toolbox. The importance of protecting fish habitat remains the same, but how we go about it will continue to change, along with the climate.

Salt marsh. Credit: NOAA/Eric Hutchins

Eel grass and mussels. Credit: NOAA/Mike Johnson