Bosque del Apache National Wildlife Refuge, © Gary Garton

Sink or Swim? Sea-Level Rise in Wildlife Refuges

Aimee Delach, Senior Policy Analyst, Climate Adaptation

As Julie shared last Tuesday, the National Wildlife Refuge System, managed by the U.S. Fish and Wildlife Service (USFWS), includes approximately 150 million acres of lands and waters managed primarily for wildlife conservation and protection of habitats. For many Americans, our national wildlife refuges are their best chance to see rare sights like huge flocks of migrating snow geese, endangered whooping cranes, and many other species.

One of the threats facing these amazing places is climate change. The effects of a shifting and increasingly volatile climate are already being felt across the U.S., and for the animals that make their homes in wildlife refuges  — including many species that are already threatened or endangered  — it represents a serious danger. One way climate change will continue to affect refuges is by a rise in sea levels, due to the melting of land-based ice and the expansion of the oceans as they warm. Recent studies suggest that sea-level rise could easily exceed 39 inches by 2100. That’s more than three feet! For the more than 150 national wildlife refuges located in coastal areas, sea-level rise has the potential to reshape wetlands, shift habitats inland and upland, and even put large parts of some refuges entirely underwater.

This is a concern, not just for the lands already protected as a part of the National Wildlife Refuge System, but also for lands that the U.S. Fish and Wildlife Service plans to add to the system. The process that USFWS uses to add land to refuges only takes the value of current habitat into account, but not how resilient the habitat can be in the face of threats like sea-level rise. Without considering the effects of climate change as part of the deciding factor of what land to buy, USFWS may not be making the best investments of their limited funds if some of that land is going to be underwater within a few decades. So Defenders’ climate team, with the help of a summer intern from Duke University, decided to look into it ourselves.

Blackwater National Wildlife Refuge Sea Level Rise Map

This is what Blackwater NWR could look like by 2075. The red area — both what they have now, and what they plan to buy — will likely be completely flooded.

We assessed the sea-level rise threat to the lands within both the acquired boundary (the land the refuge already owns) and the approved boundary (the land they are planning to acquire) of eight coastal refuges. We used a publicly-available analysis tool called the Sea Level Affecting Marshes Model (SLAMM) that shows how rising sea levels will likely change the coastal landscape. The model lets you choose from among several scenarios of sea level rise over the 21st century, which is important because we don’t yet know precisely how much the climate will warm and the sea level will rise. The model then incorporates local conditions and processes to give a site-specific picture of how each area will be impacted. This is important because conditions at each site are different. Some coastal areas have rivers that are delivering sediments at a rate that could help refuge lands “keep up” with the rise. In other places, the land is eroding, which means that the local impacts of sea-level rise will be more pronounced.

We found that the impact of sea-level rise will vary among the eight refuges we investigated. Four of the refuges could have less than 5% of their land area vulnerable, while two could lose more than 40% of their refuge lands by 2075. One of the highly impacted refuges, Blackwater NWR, may be able to keep vital habitat by buying new land on the north side, where areas of marsh will persist and new marsh will be created. Great White Heron NWR, on the other hand, could run out of land entirely; it could lose almost 90% of its current land, and three-quarters of the land it plans to acquire. That would mean the loss of nesting habitat for loggerhead and green sea turtles, as well as over 250 species of birds that call the islands of Great White Heron NWR home, including the refuge’s namesake.

Too many species of wildlife depend on our nation’s coastal refuges for us to afford to lose them. These are places that provide ecological, recreational, and economic support to their communities. But they can’t do so if they find themselves underwater. We want the USFWS to make smart conservation investments in buying new land for coastal wildlife refuges, so we’re doing more than just pointing out the problem. Based on our findings, we’re offering several recommendations:

  • Unless there is an immediate conservation need that justifies protecting a vulnerable parcel, or USFWS determines a parcel is important to allow for marsh habitats to transition or shift inland as sea levels rise, individual refuges should focus on acquiring land that is less vulnerable to sea-level rise.
  • When a vulnerable parcel needs to be protected, USFWS should consider alternatives to land purchase, such as easements, which may be a more cost-effective way to provide protections in the short term.
  • USFWS should alter approved refuge boundaries as appropriate to maximize long-term conservation benefits in the face of sea level rise. For instance, the area to the north of Blackwater NWR has wetlands that will outlast sea level rise, and moving the refuge boundary to include these would allow USFWS to protect more habitat for the long term.

We know that we face two enormous challenges as we try to protect wildlife and habitat into the future. First, climate change is posing new threats to species and altering landscapes, and in the case of coastal areas, taking some away entirely. And second, ongoing difficulties with the federal budget mean that taxpayer investment in land conservation is likely to be limited. But by understanding the effects of climate change, we can adjust our strategies to make the smartest possible investments for the future of our wildlife and the wild places they need to survive.


This table shows an overview of what we found for each of the eight refuges. To learn more, check out the report and recommendations here [PDF], or download the entire report [PDF]