Five estuary species that rely on climate resilient habitat

The adverse effects of climate change on our coastal ecosystems are a threat to local communities and fish and wildlife habitat. Luckily, through restoration and protection of these critical habitats, we can defend against some of the negative impacts. Of course, in order to fully combat climate change, we must also reduce emissions in addition to these efforts.

The good news is that often habitat restoration provides as a win-win-win for climate, the economy, as well as fish and wildlife, especially in estuaries. The same marshes that act as a buffer against storms and flooding in Southern Louisiana are home to a thriving red drum population and the gateway to the Mississippi River – one of the most important shipping and commerce routes in the world.

In honor of NOAA’s habitat month this July, we wanted to look at five species that stand to benefit greatly from habitat restoration that also improves resilience against climate change.

Atlantic Tarpon (Megalops atlanticus)

Also known as the silver king, the Atlantic tarpon is one of the most sought-after gamefish on planet earth. Reaching up to 200+ lbs, these  goliaths stretch up and down the southeast Atlantic from South Carolina through the Florida Keys and into much of the Caribbean.

Juvenile tarpon rely on the mangrove forests along the coast for protection from predators as well as the abundance of food, primarily shrimp and smaller baitfish, these ecosystems provide. As seas rise, mangroves are becoming increasingly threatened. Although they are used to being inundated with the tides, seas are rising faster than the trees are capable of surviving while human development also threatens mangroves from shore.

In addition to providing habitat for tarpon, mangroves attenuate wave energy at a rate of up to 66% and are especially valuable during hurricanes or other major storm events. They also are known to store carbon deep in the coastal soil, providing a critical sink of CO2 and helping in the fight against climate change.

Conservation status – vulnerable

Blue Crab (Callinectes sapidus)

The blue crab has become something of a deity on the Atlantic coast. A trip through the Chesapeake Bay will reveal blue crab clothing, memorabilia, and art adorning homes, shops, and town squares. Enjoying a crab feast is a staple of many summer vacations for two reasons: 1) they’re not incredibly difficult to catch – all you need is a net and some chicken gizzards – and 2) because they’re darn tasty.

Blue crabs, specifically juveniles, rely on seagrasses and other submerged aquatic vegetation and nearshore habitat for protection. Seagrass also is incredibly productive at capturing carbon, roughly 35x faster than tropical rainforests and absorbing 10% of the ocean’s carbon each year. However, the world has seen roughly 29% of its seagrass population disappear since the late 1800’s, mostly due to human development and pollution. Although many efforts to restore seagrass have been successful, they are also sensitive to changing water temperatures and are vulnerable to warming seas due to climate change.

Recreational and commercial blue crab anglers have witnessed the result of these fluctuations firsthand. Research from the Virginia Institute of Marine Sciences shows that as grass bed density has declined so have blue crab populations. In 2022, surveys in the Chesapeake Bay returned the lowest population of blue crabs in the 33-year history of the study, at 227 million – down from 281 million in 2021. However, the same survey returned high numbers of juvenile blue crabs, due to increases in seagrass density and restoration – a sign of hope for what’s to come.

Conservation status – stable

Eastern Oysters (Crassostrea virginica)

Oysters, like the blue crab, have their own cult following. Spanning the entire east coast and Gulf of Mexico, oysters have regional differences from even one bay to the next in taste due to salinity and other factors. What you may not know, though, is that these bivalves play a critical role in improving water quality. One adult oyster can filter up to 50 gallons of water a day and oyster reefs also provide criticalhabitat for some of our favorite gamefish, such as the previously mentioned red drum.

Many RAE member groups are also growing oysters for their innate ability to protect shorelines in the face of a changing climate – working with local restaurants to recycle shells and engage members of their community – a nature-based living shoreline method that has proven to be more cost-effective and successful than traditional grey infrastructure, such as sea walls and bulkheads.

Unlike some of the other species mentioned in this story, oysters themselves actually provide some solutions to climate change. In addition to protecting shorelines from rising seas, oyster populations create more opportunities for seagrass to grow by cleaning our waterways, thus leading to more carbon capture. Oysters are also resilient to changing temperatures and salinity, both expected outcomes due to warmer air temperature and drought. Since they are living creatures, they can also physically move to outpace sea level rise once healthy populations have been established.

Conservation status – stable

Chinook Salmon (Oncorhynchus tshawytscha)

The largest of the Pacific salmon, chinook, or King Salmon, are one of the most iconic species in the United States, if not the entirety of North America. Chinook are a cultural and religious icon of many of the Pacific Northwest’s indigenous tribes and a core pillar of the commercial fishing economy worth over $43 million. Healthy chinook populations rely on three things – 1) access to spawning grounds 2) cold, clean water, and 3) a healthy ocean.

Chinook migrate from their natal streams to the ocean at about one-year, spending the next 2-3 years prowling the pacific and arctic oceans for food before returning to the stream they were born to spawn. Dams and other barriers to fish passage have blocked access to many productive salmon runs, causing populations of chinook and other salmon to decline, leading to complete extirpation in some river systems.

In addition to these physical barriers, chinook salmon are fighting an uphill battle at sea and upon their return. Ocean temperatures are rising and becoming both less productive and more inhospitable due to climate change. Chinook rely on an abundance of food at sea to grow strong enough to return to their spawning grounds, a journey in which they are singularly focused on reproduction and do not eat once they enter freshwater. On land, prolonged droughts are causing streams to run warmer and dryer, causing stress for juvenile chinook as well as returning adults.

Conservation efforts to restore salmon habitat include reforestation, dam removal, and other river/estuary reconnection efforts. Trees provide shade for streams, lowering water temperatures while also sequestering carbon. Removing dams and reconnecting waterways allows rivers to naturally move sediment and nutrients downstream to estuaries. This sediment is the building block for coastal wetlands that can further sequester carbon and promote seagrass growth.

The history of salmon and their importance to the the tribes of the Northwest is too long and complex to squeeze into just a few paragraphs. For more information, here’s a helpful guide from the Columbia River Inter-Tribal Fish Commission.

Conservation status: distinct populations vary from endangered to stable – list of protected populations

Harlequin Duck (Histrionicus histrionicus)

Harlequin ducks call both the east and west coasts home. The western population chooses to winter in the Aleutian Islands of Alaska south into coastal Oregon while the eastern population holds over along the coasts of New England and the Mid-Atlantic and north into Canada. Harlequins, and many other waterfowl for that matter, consider wetlands prime wintering habitat because of the abundance of food and cover available even in the coldest months – allowing them to successful rear offspring.

Development and sea level rise are putting coastal wetlands increasingly at risk. It is estimated that the U.S. has lost more than 50% of our wetland habitat since the 1600’s, with peak losses occurring from the 1950’s to 1970’s. Due to this habitat loss, and other factors, the duck breeding population fell by 31% from the mid 1980’s to 2001, according to the National Audubon Society.

Thankfully, wetland restoration is trending upward with new science prevailing on the multitude of benefits they provide, including carbon sequestration. Federal regulations, such as the Clean Water Act, have also improved protections for critical wetland habitats. Additionally, groups like Ducks Unlimited in partnership with the federal government are updating the nations National Wetlands Inventory to better understand areas of high risk and potential to provide climate benefits.

Conservation status – least concern