Introduction

We have entered the Anthropocene, an epoch of unprecedented human-induced alteration of our planet (Zalasiewicz et al. 2008). Humans have polluted the air and oceans, facilitated exotic species invasions, and simplified ecosystems (Hooper et al. 2012; Zalasiewicz et al. 2008). However, the greatest threat to the planet’s ecology may be climate change, which is expected to alter global weather patterns, species distributions, and ecosystem function within our lifetime (IPCC 2014; Scheffers et al. 2016). Many of these effects already are being felt (Soja et al. 2007; Rowe et al. 2015; Trenberth et al. 2015). Temperatures are already rising, leading to the melting of polar ice caps and expanding water volume in the oceans (Gornitz et al. 1982; Mörner 2017; van den Broeke et al. 2016). These conditions put coastal areas at increased risk with entire ecosystems predicted to be lost or redistributed due to sea-level rise (Nicholls and Cazenave 2010). It is easy to question the value of research and conservation efforts if the loss of conserved areas, particularly in low-lying coastal zones, is inevitable (Table 1; Swaisgood and Sheppard 2010). Should we instead focus our limited resources on areas that face less dire consequences and possess a higher “probability for success” as some champions of conservation triage suggest (Hobbs et al. 2003; Bottrill et al. 2008)? For example, perhaps restoration programs should prioritize areas at higher elevations over those more likely to be lost to sea-level rise (Courchamp et al. 2014; Southeastern Association of Fish and Wildlife Agencies 2019). Or should conservation of low-lying areas remain a priority despite the threat of sea-level rise (Andréfouet et al. 2015; Kench et al. 2018)?

Table 1 Evidence of de-prioritization of low-lying coastal areas for research, management, restoration, and conservation
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Extensive resources have been allocated by public and private entities to sustain coastal areas that are at risk of future inundation (Stein et al. 2014; Epanchin-Niell et al. 2017). However, some low-lying coastal areas are being de-prioritized for conservation, restoration, management, and research because they are likely to be lost or degraded (Table 1). In the USA, the federal response to coastal inundation has been muted by the politicization of climate change (Trump 2017; Selby 2019; Chinn et al. 2020) resulting in programs dedicated to coastal research, restoration, conservation, and resiliency planning being recently stripped of funding or eliminated entirely (Department of the Interior 2020; Office of Management and Budget 2020; Office of the Chief Financial Officer 2020). Budgetary shortfalls related to the COVID-19 pandemic are expected to further exacerbate this trend (e.g., McCleery et al. 2020; California Department of Finance 2020; Office of the City Manager 2020). Now, as signs of climate change increase in tandem with reduced funding, we face an unprecedented challenge to save fragile ecosystems.

As early-career scientists in Florida (USA), we are often challenged by colleagues, friends, family, and the public to defend our research and the investments made to the conservation of imperiled species and ecosystems. Florida is a low-lying state with extensive, biologically diverse tidal shorelines and world-famous wetlands. Much of this may be lost by 2100 if sea levels rise by 2 m (Southeast Florida Regional Climate Change Compact Sea Level Rise Work Group 2015; Fig. 1). Using sea-level rise (hereafter, SLR), “the most immediate, the most certain, the most widespread, and the most economically visible” effect of a changing climate (Pilkey and Young 2009, pp. 203), we first highlight the ecological and societal benefits of low-lying ecosystems. We then use Florida as a case study to present arguments for why continued scientific engagement in these vulnerable ecosystems is so important, what we stand to lose from abandoning coastal ecosystems, and what gains can be made from studying and protecting low-lying ecosystems. Despite discouraging projections, we urge other early-career scientists to continue to advocate for research and conservation in ecosystems most vulnerable to SLR.

Fig. 1
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Examples of coastal conservation areas predicted to experience major losses and ecosystem change due to sea-level rise in Florida, USA (black star): (a) Eglin Air Force Base, (b) Waccasassa Bay Preserve State Park, (c) Everglades National Park, and (d) the Florida Keys. The amount of land area that is predicted to be covered by 2 m of sea-level rise by 2100 is based on elevation alone and does not account for potential additive effects (National Oceanic and Atmospheric Administration 2012)

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Importance of Low-Lying Ecosystems to the Earth and to Society

Sea levels are projected to rise globally between 0.5 and 2.0 m by the turn of the century (Church et al. 2013; IPCC 2014; DeConto and Pollard 2016). The consequences of SLR will be most noticeable in low-lying coastal areas and islands worldwide (Reece et al. 2013; Schmidt et al. 2012), threatening many of the ecosystem services these areas currently provide (Nicholls 2011). Approximately 23% of the global population lives within 100 km of a coast (Small and Nicholls 2003), and over 600 million people live below 10 m above sea level (McGranahan et al. 2007). Coastal zones with high population density, low elevations, high rates of land subsidence, and limited adaptive capacity are predicted to be at the greatest risk from SLR (Nicholls and Cazenave 2010). For example, changes to ecosystems (e.g., erosion, flooding) in low-lying atoll nations are expected to render many of these islands uninhabitable (Roy and Connell 1991; Nicholls and Cazenave 2010; Hubbard et al. 2014).

Marked changes to coastal ecosystems due to SLR may be inevitable. Nevertheless, maintaining and restoring healthy, functioning ecosystems through science-based decision-making and conservation actions is more important than ever. Low-lying coastal areas provide critical ecosystem services such as water filtration, barriers against coastal erosion, and habitat for wildlife (Millennium Ecosystem Assessment 2005; Kirwan and Megonigal 2013; McKee et al. 2007). Coastal marshes, mangroves, oyster reefs, and other littoral communities (e.g., seagrass beds and coral reefs) reduce water velocities and flooding from storms (Arkema et al. 2013; Temmerman et al. 2013). Further, corals and mangroves act as foundational species by supporting thousands of other species (Ellison et al. 2005; Ellison 2019), such as many seabirds that nest on low-lying barrier islands (Spatz et al. 2014). Vegetated coastal ecosystems also mitigate future climate change by sequestering organic carbon, accounting for approximately half of all carbon stored in ocean sediments (Duarte et al. 2013). Protecting and restoring the functionality of these ecosystems will not only reduce the local effects of SLR but will also help to reduce climate change globally.

Healthy coastal ecosystems confer considerable economic value. Tourism drives many national and local economies as millions of tourists visit unique coastal ecosystems and coastal world heritage sites every year (Cui et al. 2013; Dehoorne and Tatar 2013; Ghermandi and Nunes 2013). Ecotourism activities centered around coastal ecosystems such as fishing and wildlife viewing generate billions of dollars annually (Brodie and Pearson 2016; National Marine Fisheries Service 2016; Southwick Associates 2011), and property values tend to increase with proximity to natural areas (Cape Ann Economics 2003; Correll et al. 1978). Healthy commercial fisheries also support livelihoods in coastal communities (National Marine Fisheries Service 2016). As the ecosystems on which these activities depend continue to degrade due to SLR, our local, regional, and national economies will suffer. Annual losses in ecosystem services due to degradation and decline of the world’s wetlands, many of which are found in low-lying coastal areas, are estimated to exceed US$20 trillion (Gardner et al. 2015).

Functional coastal ecosystems also provide opportunities for the public to learn about and develop a connection to nature. For example, millions of people visit the 180 coastal refuges in the US National Wildlife Refuge System each year, where they learn about the estuarine, ecological, and biogeochemical processes that govern these wetland ecosystems (United States Fish and Wildlife Service 2012). Rare, unique flora and fauna occurring in ecosystems susceptible to SLR also inspire fascination, art, and photography around the world (Orlean 1998; Matilsky 2018; Petri 2016). Educational and artistic opportunities provided by healthy coastal systems will be lost if we abandon or allow these areas to potentially degrade. Further, degraded ecosystems may be perceived as normal and become the new standard for conservation efforts (i.e., shifting baseline syndrome; Papworth et al. 2009). Consequently, a true understanding of healthy ecosystems and associated conservation ethics will not be passed along to future generations (Jackson 1997; Papworth et al. 2009; Pauly 1995).

Coastal ecosystems, like all wild places, possess an inherent or intrinsic value that deserves protection for their esthetic, historical, and cultural significance, and not for any monetary value they confer to humans (Soulé 1985; Taylor 1986). Species represent unique evolutionary lineages (e.g., the island fox [Urocyon littoralis], endemic to the Channel Islands of California, Goldstein et al. 1999), and ecosystems represent unique assemblages in time and space (e.g., the Great Barrier Reef and its astounding biodiversity have evolved over the past 600,000 years; Flood and Heatwole 1986; Gray et al. 1992; Planes and Doherty 1997). This intrinsic value is particularly important for species or ecosystems with little apparent economic value that otherwise may receive low conservation priority. By continuing to conserve, learn from, and restore vulnerable ecosystems, we can protect the many values provided by these ecosystems and the species within them for as long as possible.

What We Stand to Lose: Florida as a Case Study for Low-Lying Ecosystems Worldwide

Florida represents the acute challenges faced by conservation biologists working in low-lying coastal ecosystems worldwide and is especially vulnerable to encroaching seas (Fig. 1). Florida is a biodiversity hotspot at the intersection of temperate and tropical biomes with vast expanses of fragile ecosystems that are found around the world including coral reefs, mangroves, coastal forests, tree islands, grasslands, salt marshes, estuaries, sand dunes, and tidal flats (Myers and Ewel 1990). Like many other coastal areas worldwide, Florida’s coastline has seen enormous increases in development and economic growth fueled in part by tourism. With 3660 km of tidal shoreline (Donoghue 2011), thousands of barrier islands, an average elevation of only 30 m (Carpenter and Provorse 1996), and approximately 10% of land area less than 1 m above sea level (Weiss and Overpeck 2003), many of Florida’s human and natural ecosystems will be directly harmed by SLR.

Current models project that many of Florida’s coastal ecosystems will be inundated by SLR, which will reduce, eliminate, or alter the spatial distribution of estuaries, beaches, mangrove forests, and salt marshes (Noss 2011; Zhang et al. 2011; Fig. 1). Additionally, coastal areas that remain are likely to be degraded from saltwater intrusion (Saha et al. 2011; Williams et al. 1999), coastal erosion, and higher storm surges (Pilkey and Young 2009). Currently, Florida has one of the highest rates of species endemism in North America (Maltby and Dugan 1994; Estill and Cruzan 2001; Sorrie and Weakley 2001). With many species dependent on coastal ecosystems, Florida’s wildlife is extremely vulnerable to SLR (Reece et al. 2013; Box 1). One meter of SLR threatens to inundate nearly all of Everglades National Park (Noss 2011; Fig. 1c), endangering at least 21 rare species in this world heritage site (Saha et al. 2011). With a 1.5-m rise in sea level, the Florida Keys may be 91% inundated (Zhang et al. 2011), with concurrent losses of the region’s many endemic species (Maschinski et al. 2011; Reece et al. 2013; Schmidt et al. 2012; Fig. 1d; Box 1). For example, remnant populations of unique orchid species face increased habitat deterioration from SLR and hurricanes (Raventós et al. 2015). As sea levels rise, ecosystems will experience shifts in distribution and composition (Geselbracht et al. 2011), including transitions from coastal forests to saltmarsh and from inland forests to tidal flats. Species reliant on coastal vegetation communities face extinction or regional extirpation if unable to migrate inland (Geselbracht et al. 2011; Hoctor et al. 2010; Maschinski et al. 2011; Oetting 2010; Ross et al. 2009). While Florida’s coastlines have expanded and contracted for millions of years (Donoghue 2011), those changes were not coupled with anthropogenic habitat alteration. Florida’s widespread coastal development will prevent many coastal species from moving inland (Schmidt et al. 2012). Human migration inland from coastal cities will further diminish the availability and continuity of remaining refugia (Hoctor et al. 2010; Noss 2011), impeding wildlife dispersal (Davis and Shaw 2001).

Box 1
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Examples of species predicted to be severely affected by habitat loss and changes associated with sea-level rise in Florida. Species predicted to be extinct by 2100 with ≤ 2 m of sea-level rise and other synergistic effects (Reece et al. 2013): (a) Florida grasshopper sparrow (Ammodramus savannarum floridanus) (b) Bartram’s scrub-hairstreak (Strymon acis bartrami) and (c) Key ringneck snake (Diadophis punctatus acricus). Species that are likely vulnerable to sea-level rise due to restricted ranges: (d) Florida bonneted bats (Eumops floridanus) are endemic to south Florida and federally endangered, (e) the Sanibel Island rice rat (Oryzomys palustris sanibeli) is endemic to Sanibel Island and has low population densities, (f) lower keys marsh rabbits (Sylvilagus palustris hefneri) are endemic to the lower Keys and are federally endangered. Photo credits: (a) RSCF/www.rarespecies.org, (b and c) Jonathan D. Mays (d) Elizabeth C. Braun de Torrez, (e) Wesley W. Boone, (f) Chad Anderson/ United States Fish and Wildlife Service

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What We Stand to Gain from Continued Research and Conservation in Low-Lying Ecosystems

While major changes to coastal ecosystems in Florida and across the globe will most certainly occur, many questions remain. We face important knowledge gaps about (1) the spatiotemporal uncertainty surrounding SLR, (2) the resistance and resilience of species and ecosystems, (3) how to best mitigate the effects of SLR, and (4) the effectiveness of adaptive management techniques—all of which could be better understood by continued research and conservation in low-lying ecosystems (Table 2). This information is critical for understanding and mitigating climate change both locally and globally.

Table 2 Examples of outstanding knowledge gaps that will help us better understand and prepare for the effects of sea-level rise (SLR) on vulnerable coastal species and ecosystems
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Remaining Uncertainty and Questions About Sea-Level Rise and Its Ecological Effects

Spatiotemporal Uncertainty Surrounding SLR

Perhaps most critically, scientists remain uncertain about the spatial variation, timing, rate, and magnitude of projected SLR (Miller and Douglas 2004; Nerem et al. 2018; Noss 2011; Sukop et al. 2018). Predictions of SLR and resulting impacts on ecosystems vary considerably depending on different emission scenarios and ecological factors (DeConto and Pollard 2016; Church et al. 2013). For example, if sea levels rise 0.64, 1, or 2 m by 2100, the Waccasassa Bay region of Florida’s gulf coast could experience net losses of 69%, 83%, or 99% in coastal forests but net gains of 17%, 142%, or 3837% in tidal flats, respectively (Geselbracht et al. 2011; Fig. 1b). Similarly, estimates of change to coastal ecosystems at six major Florida estuaries vary greatly in magnitude, and even direction, depending on the level of predicted SLR (Geselbracht et al. 2015). Factors such as erosion, vegetation community composition, and the health of vegetation communities further complicate our ability to accurately predict future conditions (Geselbracht et al. 2011). For example, depending on model parameterization, Chu-Agor et al. (2011) found that the extent of low-elevation habitats such as salt marshes and beaches at Eglin Air Force Base in Florida could either decrease or increase over the next 100 years (Fig. 1a). Such uncertainty regarding the extent, composition, and health of future coastal areas makes it difficult to predict the persistence and magnitude of future ecosystem services provided by these areas (Kirwan et al. 2016). Before we can effectively prioritize conservation areas and develop appropriate responses, we need to refine our predictions of which specific areas will be impacted by SLR, how much SLR will actually occur in those places, and how far into the future we should expect these changes to occur.

Resistance and Resilience

Even if we were completely sure of the spatial variation, rate, and magnitude of SLR, we do not fully understand how species and ecosystems will respond to the associated changing conditions. The complex effects of SLR on factors such as species’ ability to adapt and move, interspecies interactions, and their resulting effects on ecosystems and how well ecosystems are able to function under changing conditions remain uncertain yet are key to determining the vulnerability of species and ecosystems (Reece and Noss 2014; Reece et al. 2013). For example, low-lying atoll reef islands in the central Pacific, commonly considered to be doomed by SLR, may actually increase in land area as they accrete vertically and change shape in response to shifting sediments, if they are not impeded by development (Webb and Kench 2010; Kench et al. 2018). Similarly, coral reefs in Tahiti appeared to avoid reef drowning during the last deglaciation period by rising in tandem with rapidly rising seas (Camoin et al. 2012), and the Marshall Islands were formed under rising sea levels (Kench et al. 2014). It is unclear how barrier islands and coral reefs in Florida will respond to SLR, but their response and resiliency depend on many factors, including recovery from storm events, sediment texture, and damage incurred from coral bleaching and disease (Maynard et al. 2015; Perry et al. 2018), and thus can be expected to vary regionally depending on geology (e.g., Houser et al. 2018). Andréfouet et al. (2015) contend that the number of islands predicted to be completely drowned is grossly overestimated because simplistic models assume that islands are passive geological entities rather than dynamic landforms able to respond to SLR.

Species and ecosystems will likely respond differently to SLR. Some species may respond quickly if they are able to adapt (e.g., physiologically) or move inland, shifting community composition to favor species better suited for the new conditions (Smith et al. 2009). For example, landward migration of some mangrove trees and coastal marsh grass may be able to keep pace with slow rates of SLR (Gilman et al. 2008; Kirwan et al. 2016), giving marshes and mangroves a competitive advantage over plants which are intolerant of inundation and saltwater intrusion. On Florida’s Gulf Coast, historic SLR has led to net tidal marsh expansion (Raabe and Stumpf 2016), and models of 1-m SLR predict net increases of marshes (e.g., tidal freshwater, brackish, salt) and mangrove forests, with decreases in other coastal communities (e.g., cypress swamps, inland freshwater marshes, coastal forests; Geselbracht et al. 2015). Changing ocean conditions and SLR are likely to alter many interacting processes, such as biogeochemical cycling, disturbance regimes, and population dynamics, which will in turn impact ecosystem resilience, structure, and function (Grimm et al. 2013; Doney et al. 2012). For example, losses in ecosystem connectivity among mangroves, coral reefs, and parrotfish affect the resiliency of coral reefs to recover from hurricane disturbance (Mumby and Hastings 2007). These types of alterations to ecosystem function can be difficult to predict without first understanding the complex ecology of these ecosystems. Until we better understand the consequences of different ecosystem responses and the underlying processes, we will not know how resilient ecosystems will be in the face of SLR.

Research Needs to Better Prepare Coastal Ecosystems for the Effects of Sea-Level Rise

Once we better understand how species and ecosystems will respond to SLR, we need to determine the most effective conservation strategies going forward for both existing ecosystems and newly aggregated communities. As conservation scientists, we need to fill critical research gaps to understand how to reduce the effects of SLR on species and ecosystems and develop local adaptation strategies to minimize adverse ecological effects of SLR if mitigation is not possible. These research findings can then be used to inform conservation efforts for similar ecosystems worldwide.

Mitigating Effects of SLR

First, we need to identify the most effective ways to improve and restore the health and resiliency of existing coastal ecosystems to protect the critical ecosystem services they currently provide (Erwin 2008; Zedler 2016). Maintaining healthy coastal ecosystems will help protect adjacent land from erosion and reduce the potential impacts of SLR. To do this, we must develop effective tools to remove invasive species, restore native species, and protect these areas from development and other stressors. Ecosystems that are partially inundated by SLR will need even better management because the impact of exotic species is likely to become greater in shrinking, fragmented habitats (Andréfouet et al. 2015). In Florida, Burmese pythons (Python molurus bivittatus) have caused precipitous declines in mammal populations and threaten the ecological functioning of the entire Greater Everglades Ecosystem (McCleery et al. 2015); control of pythons is increasingly important as their impact on faunal communities will likely be exacerbated as habitat is constricted with SLR. Many scientists and land managers working to conserve Florida’s vulnerable coastal areas and species are committed to improving ecosystem resiliency through restoration efforts and available silvicultural and hydrological tools (Mark Danaher, US Fish and Wildlife Service, pers. comm.). For example, the Comprehensive Everglades Restoration Program, which represents the largest wetland restoration effort in the world, is directly combating increased SLR and salinity through the restoration of freshwater flow (Dessu et al. 2018). The threat of SLR makes the protection of estuaries and threatened and endangered species even more critical (Kim Dryden, USFW, pers. comm.). Rather than taking the attitude that these areas are going underwater so they are undeserving of our attention, scientists working in these areas view restoration planning and investment in coastal areas as even more valuable in the face of SLR (Lori Miller, US Fish and Wildlife Service, pers. comm.).

Adaptive Management

Increasing storm surges and SLR will ultimately render certain areas uninhabitable by humans as SLR outpaces restoration efforts (e.g., Dessu et al. 2018) and coastal areas cannot be raised above the approaching water. Coastal communities may need to adapt by migrating inland or to higher ground. Noss et al. (2014) suggested that the most viable adaptation strategy for many natural coastal communities in Florida may be protection and restoration of their current extent in order to facilitate natural and assisted species migration. With a vast network of conservation areas along the coasts and in the interior (~ 4,000,000 ha) and the largest taxpayer-funded conservation land acquisition program in the USA (Florida Forever; Mercas 2016), Florida is capable of improving existing areas and purchasing new lands to achieve this goal.

As scientists, we have the opportunity to identify critical current and future inland ecosystems, including migration corridors, in order to prioritize the use of limited conservation resources (Zhu et al. 2015; Roberts and Hamann 2016). However, we need continued research to understand species’ and ecosystems’ capacities to adapt to new environmental and ecological conditions, as we still do not know the current habitat associations and basic ecological requirements of many species. For example, we know little about the habitat associations of the federally endangered Florida bonneted bat (Eumops floridanus), a species endemic to South Florida that is of high conservation value and likely vulnerable to sea-level rise and other environmental changes (Reece and Noss 2014; Box 1d). Without information on roost structure and habitat preference (Braun de Torrez et al. 2016), conservationists cannot delineate and protect future refugia for bonneted bats to help reduce the effects of SLR. Additionally, recent evidence indicates that Sanibel Island rice rats (Oryzomys palustris sanibeli), confined to an island < 1.5 m above sea level (Florida Fish and Wildlife Conservation Commission 2013; Box 1e), inhabit mangrove marshes (Boone unpublished data) in addition to freshwater wetland habitats (Humphrey et al. 1986). However, as sea levels rise, we do not know if this subspecies can survive exclusively in mangrove marshes as freshwater becomes scarce. Detailed information on habitat associations, species’ occurrences, and movement patterns are necessary so that we can inform conservation strategies for species in threatened ecosystems. Further, we need to determine if currently protected ecosystems are likely to shift in range; if so, we need to consider the feasibility and value of extending the protected areas’ boundaries and removing barriers that may impede species migration. Our continued engagement in the research, conservation, and management of threatened ecosystems may slow their rate of decline.

Conclusions Regarding the Road Ahead

There is little doubt that we will see a dramatic anthropogenic environmental change in our lifetime. Due to the remaining uncertainty about ecosystems’ and species’ responses to climate change, we find ourselves trying to make decisions in a continuously changing environment. Although extremely challenging, these uncertainties leave room for optimism, research, and conservation actions that are critical for sustaining the viability of our planet and its incredible biodiversity. We argue that continuing to actively engage in research, conservation, and restoration of the most imperiled ecosystems for as long as possible confers many immediate and long-term benefits at both the local and global scales. We need to give at-risk ecosystems a chance to respond and adapt, as well as give ourselves time to develop strategies to reduce climate change effects when possible and/or adapt when needed. Remaining engaged in these ecosystems even if they are ultimately lost will provide invaluable insight into the complex effects of climate change, enabling scientists to develop more effective mitigation, adaptation, and decision-support strategies for similar ecosystems in other parts of the world. However, this is largely dependent on persuading the public and our politicians to invest in the protection of natural areas as the first and most important line of defense against SLR. There is far too much at stake to give up prematurely. We encourage scientists, particularly students beginning their careers, to face this unprecedented challenge with determination, creativity, and solution-based strategies.