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October 16, 2019
Designer: Mel Barnard
Our nation’s “gray,” or hard, manmade infrastructure is in need of repair and upgrading due to age, deferred maintenance, and the toll of more intense and frequent extreme weather events resulting from climate change. The American Society of Civil Engineers (ASCE)—which has graded the condition of the country’s public infrastructure as a D+ for nearly a decade—estimates direct, cumulative gray infrastructure repair needs at $4.6 trillion through 2025, with an estimated funding gap of $2.1 trillion. Infrastructure has long been an area of bipartisan agreement, and the 116th Congress and White House continue to allude to a possible infrastructure bill or package. As discussions take shape on the future of the country’s infrastructure, it is important to ensure projects are cost-effective, sustainable, and resilient to the impacts of climate change.
Although infrastructure is often thought of as manmade structures and buildings, it can also include natural systems, such as wetlands, and systems that emulate nature, such as green roofs. As policymakers fund improvements to the nation’s infrastructure, natural systems and solutions, referred to as nature-based solutions, should also be considered critical infrastructure. Currently, the 116th Congress is incorporating some of these nature-based solutions into a variety of legislation, including the Living Shorelines Act of 2019, the Climate Stewardship Act, and the American Transportation Act of 2019.
Extending the definition of infrastructure to include natural systems provides an opportunity to work with nature and employ nature-based solutions to create sustainable, climate-resilient solutions to the country’s infrastructure needs. These nature-based solutions are often higher-quality, lower-cost, more resilient, and more beneficial to society than maintaining, repairing, or replacing gray infrastructure. Therefore, nature-based solutions can help the United States meet the infrastructure investment gap in a cost-effective manner, while producing substantial social, economic, and environmental co-benefits. Combining gray infrastructure and nature-based solutions, often referred to as a hybrid approach, can also provide a favorable avenue for rethinking and remodeling our nation’s infrastructure.
By surveying definitions of nature-based solutions and providing specific examples of solutions and projects, this fact sheet contributes to the national conversation about two critical policy issues: how to fix America’s crumbling infrastructure and how to make communities more resilient to climate impacts.
Nature-based solutions are intended to address infrastructure needs, protect from climate impacts, and act as hazard mitigation tools (also referred to as ‘pre-disaster mitigation’). However, there is no universal definition for nature-based solutions; organizations define it in different ways and employ different terminologies.
Definitions of nature-based solutions include:
The terms green infrastructure and natural infrastructure are similar to nature-based solutions. They are sometimes used interchangeably with nature-based solutions, and other times as more specific concepts that fall under the larger nature-based solutions umbrella. They also do not have universal definitions.
This fact sheet’s terminology is informed by this set of definitions and closely follows The Nature Conservancy’s definitions of nature-based solutions, green infrastructure, and natural infrastructure. EESI uses nature-based solutions as an umbrella term with green infrastructure and natural infrastructure being sub-categories of nature-based solutions.
Developing climate-resilient infrastructure is of utmost importance as climate change impacts—such as increasing temperatures, severe weather events, and sea level rise—become more common. Nature-based solutions are beneficial infrastructure options because they have a smaller carbon footprint than gray infrastructure and often sequester carbon. This fact sheet focuses on nature-based solutions that not only address the challenge of outdated gray infrastructure, but also increase an area’s resilience to climate impacts and contribute to climate mitigation efforts. This dual effect of nature-based solutions is particularly important because, without significant reductions in greenhouse gas emissions, climate impacts will become worse, causing more severe impacts on the nation’s infrastructure.
Coastal communities are experiencing the effects of climate change, including sea level rise, more intense storms, flooding, and erosion. Coastal flooding has more than doubled in the past 30 years, according to the Climate Science Special Report by the U.S. Global Change Research Program. Additionally, due to sea level rise, high tides are becoming higher and higher, and the highest tides—king tides, which usually occur seasonally—are projected to become daily high tides, leading to even further flooding. On top of this, gray infrastructure built to “control” flooding, especially in the face of extreme weather, is increasingly failing to do its job. Hurricanes Michael (2018), Maria (2017), Irma (2017), and Harvey (2017) created a total of $290 billion in damages, forced communities to evacuate, and caused more than 3,000 associated fatalities across the United States and Caribbean countries.
Climate change impacts require a re-evaluation of infrastructure solutions. Studies suggest coastal nature-based solutions can mitigate flood and storm damage more effectively than gray infrastructure alone, and are more resilient. For these reasons, coastal states are investing in natural infrastructure solutions:
These natural infrastructure solutions are generally cost-effective, depending on the specific site. For many locations along the Gulf of Mexico, wetland and reef restoration have been found to save $7 in “flood reduction benefits” for every $1 spent on restoration, and it is estimated that nature-based solutions could help “avert more than 45 percent of the climate risk over a 20-year period, saving the region more than $50 billion in flood damages.” Across the United States, coastal wetlands are estimated to provide $23.2 billion in storm protection annually. One case study determined that, with regards to Hurricane Sandy (2012), coastal wetlands prevented an estimated $625 million in property damages. Annually, in the Northeastern United States, coastal wetlands provide a 16 percent reduction in flood damages. Another study found that combining gray infrastructure with nature-based solutions was the most effective method for mitigating flooding while providing the greatest co-benefits, saving $225 million in damages for a 1-in-100 year storm event at Howard Beach, Queens, New York. Additionally, initial costs for nature-based solutions are often cheaper than for gray infrastructure alternatives. As of June 2019, living shorelines, which last longer and do not require as many or as intensive repairs, on average cost $361/linear foot, which is a third of the $1,022/linear foot cost for concrete bulkheads.
Coastal nature-based solutions provide a slew of co-benefits, such as carbon sequestration, water quality improvement, erosion reduction, habitat provision, and support for recreation and tourism industries. For example, oyster reefs are estimated to provide services of almost $40,000/acre annually, including water quality improvement and erosion reduction. Each year, 1 square mile of salt marshes stores carbon equal to 76,000 gallons of gasoline.
As a result of increased temperatures and rainfall due to climate change—combined with a reduction of natural landscapes and an increase of impermeable surfaces due to development—many regions are experiencing more frequent and intense flooding. From rural areas and farmlands to urban centers, flooding spreads pollution, creates public health concerns, damages infrastructure, kills crops, damages farms, affects individuals’ livelihoods, and causes more than 100 fatalities in the United States each year. Additionally, floods are expensive. From 1998 to 2014, the Federal Emergency Management Agency (FEMA) provided $48.6 billion in grants for infrastructure repairs, and between 2007 and 2017, the National Flood Insurance Program (NFIP) on average paid $2.9 billion annually in flood-related losses. These damages come from riverine flooding and overflow from storm drainage systems (discussed in this section) and coastal flooding (discussed in the section above). Because floods are so costly and have so many negative impacts, it is deeply concerning that flooding is projected to increase and floodplains (areas that experience flooding) are estimated to expand 45 percent by 2100.
While gray infrastructure exacerbates flooding in many cases, and is costly to update to handle increased water flow, nature-based solutions can help mitigate flooding from overflowing rivers and storm drainage systems in cost-effective ways. According to the National Institute of Building Sciences, federal funding for riverine flood reduction can save $7 in avoided damages for every $1 invested. While a comparable federal analysis does not exist for flooding from storm drainage systems, many cities have completed assessments estimating green infrastructure projects would be significantly cheaper in the long term than upgrading or building gray infrastructure. In Los Angeles, a storm drainage system retrofit project is estimated to cost between $2.8 and $7.4 billion for green infrastructure, compared to approximately $44 billion for traditional gray infrastructure. In Philadelphia, implementing a new green infrastructure plan would cost $1.2 billion over 25 years, whereas a comparable gray infrastructure plan would cost $6 billion.
According to an EPA study of 20 watersheds that are projected to grow between 2020 and 2040 due to increased precipitation and development, using green infrastructure to mitigate flooding from storm drainage systems can save hundreds of millions of dollars. However, the solutions a community employs depends on its specific location, existing infrastructure, and the type of flooding it faces—either riverine or from storm drainage systems—so all potential solutions should be evaluated in context before being implemented.
Green infrastructure solutions can often be used to mitigate both types of flooding, while natural infrastructure is generally more applicable to riverine flooding. Additionally, it is important to note that these strategies can be used by coastal communities to help mitigate flooding as well.
By reducing runoff and increasing filtration, these green and natural infrastructure strategies help to minimize water pollution. This improves water quality, and can reduce water treatment costs by 25 percent or more. Planting native plants can help reduce the usage of chemical fertilizers, further improving water quality. This provides public health benefits because people are less exposed to polluted water and drinking water contaminants. Rain gardens, bioswales, permeable pavements, and natural infrastructures can help replenish groundwater supplies by absorbing and filtering water. The solutions that involve plants/ecosystems sequester carbon, helping to mitigate climate change. Additionally, many of these solutions also help reduce extreme heat, as discussed in the section below.
According to a 2019 report from the Union of Concerned Scientists, the frequency and severity of extreme heat is projected to grow over the coming decades as a result of climate change, bringing with it health and safety risks. Already, extreme heat is the leading cause of weather-related deaths, claiming more than 600 lives annually. Under a business-as-usual scenario, by 2050, 150 U.S. cities, compared to three cities at present, will experience 30+ days each year with a heat index above 105°F, leading to even more heat-related illnesses and deaths. Even if greenhouse gas emissions are slowly reduced, by 2050, 80 cities will still have 30+ days each year with a heat index above 105°F.
Gray infrastructure, and particularly roads, parking lots, and buildings, exacerbate extreme heat because they reduce moisture in the air and absorb more heat than vegetation does. One way to locally adapt and help keep people and other species safe from extreme heat is to implement nature-based solutions that help lower temperatures in developed areas. Green infrastructure solutions that are useful in mitigating flooding—discussed in the above section—also can help mitigate heat. These solutions include:
In addition to the co-benefits related to water usage noted in the section above, these nature-based solutions help improve air quality by reducing air pollution and smog. This helps improve public health and reduces risks for respiratory problems such as asthma. Additionally, lower temperatures lead to less money and energy being spent on cooling costs. This helps save money for individuals and businesses, and also lowers emissions, helping to mitigate climate change. These solutions also provide habitat for a variety of species.
While context specific, the widespread implementation of nature-based solutions is a critical tool for addressing U.S. infrastructure needs in the face of climate change. Importantly, nature-based solutions generally do not increase greenhouse gas emissions, unlike gray infrastructure that is produced from energy-intensive materials (energy derived from fossil fuel combustion that emits greenhouse gases).
Around the country, organizations and communities are employing nature-based solutions, and the federal government is increasingly prioritizing nature-based solutions as well. For example, the US Fish and Wildlife Service Coastal Program is currently working on a plethora of projects, including restoring salt ponds to wetland habitats in the Don Edwards San Francisco Bay National Wildlife Refuge, supporting living shoreline development in many counties along the Florida coastline, and removing the Pond Lily Dam to restore natural stream flow and mitigate flooding in New Haven, Connecticut. The U.S. Army Corps of Engineers’ Engineering with Nature program works with communities around the country to combine natural and gray infrastructures.
Nature-based solutions are becoming more prevalent and widely accepted as infrastructure solutions to climate change. The federal government has the opportunity to build on this momentum through legislation, appropriations, and project management. To increase resilience to climate impacts, nature-based solutions should be seen as critical infrastructure, helping mitigate climate change and protect our communities.
Author: Heather Luedke
Editor: Anna McGinn