Defining Resilience

The anthropogenic modification of Earth and Earth systems has, in recent years, garnered attention from a variety of academic disciplines resulting in increased awareness and interest in resiliency across multiple system types that include ecological and social systems. Generally, resilience is the amount of disturbance a system can absorb without changing state (Gunderson 2000, 426). However, resilience can be defined differentially by various disciplines: social scientists define social resilience as comprising three dimensions—coping capacity, adaptive capacity, and transformative capacity (Keck and Sakdapolrak 2013, 5–7). Ecologists measure ecological resilience by the magnitude of disturbance that can be absorbed by a system before its variables and processes controlling the system’s behavior are changed such that the system redefines its structure or settles in an alternate stable state (Gunderson 2000, 426). Ecologists also identify systems designed with a single operating objective and a global optimum where alternate states should be avoided as engineering resilience (Gunderson 2000, 426).

There is potential for sustainability where resilient social and ecological systems meet and shape one another through various interactions. Sustainable resilient systems promote societal use of ecosystem services supporting contemporary societal needs without risk to future generations (Adger and Hodbod 2013). It is possible for seemingly appropriate and rational decisions from individuals, and society at large, to be counter to long-term sustainable solutions, even to the point where the resiliency of the support systems that promote such decisions is disrupted (Kahn 1966, 23, 24, 27). The consequences of known and unknown socio-ecological risks to the present and the future are diminished where resilient systems support sustainability (Adger and Hodbod 2013, 79–81). Risks that may be mitigated include changing climate, natural disasters, and wholesale socio-political systems change (e.g., abolition of slavery).

Alternate stable states theory suggests a resilient system can exist in more than one state. A state is considered stable when the disruptive variables influencing it are not so disruptive that it shifts state or regimes. The resiliency of a system determines how large of a perturbation the system can experience without the system shifting states. Stable state theory is commonly visualized with a cup-and-ball diagram (Fig. 1), where the “cup” represents the system, and the ball represents the state of the system. The parameters maintaining the system state are represented by the walls of the cup; the position of the ball in the cup represents the state of the system. When the ball is at the bottom of the cup (i.e., the basin of attraction) the system is most stable. The steepness of the walls determines the return time of the system after disturbance, whereas the width of the cup pertains to the system’s resilience. Negative feedback mechanisms tend to push the system back towards the stable bottom of the cup after a perturbation. For the system to change to an alternate state, the perturbation must be large enough for the ball to breach the precipice of the cup and enter another stable state. Once an alternative stable state has been entered it is unlikely that the previous stable state can be reclaimed.

Fig. 1
figure 1

Characteristics of socio-ecological stable states are represented by the various components of the cup-and-ball diagram. The state of the system is represented by the ball, while the parameters that control the system’s state are represented by the walls of the cup. In the figure presented there is a transition era where the precipice of the original state (i.e., Era of “rice culture”) has been breached and the system is gaining momentum towards transitioning to the contemporary era but there are a variety of forces attempting to push the system’s state back into the stability of the era of “rice culture”. We refer to this era as a transition era

Full size image

Resilience on Lowcountry Wetlands and in Lowcountry Rice Fields

The economic, cultural, and environmental significance of southeastern rice is almost completely obscured by that of King Cotton, the export crop that came to dominate southern agriculture by the mid-1800s. Even still, the role of rice agriculture is almost completely unknown to the American consciousness as the driving national force it once was, one that created the wealthiest planters and largest slaveholders in British North America before the American Revolution. South Carolina rice planters claimed Nathaniel Heyward, the wealthiest slave holder with the largest slave holdings, as one of their own until his death in 1851 (Heyward 1993, xi, liv, 3–6, 12–13, 18–19). The value of rice to global society has been and continues to be immense.

Across time and space, Queen Rice can demonstrate how human labor and wetlands can be harnessed for economic ends, and how such systems can be resilient or collapse with political change such as that of the 13th Amendment of the US Constitution. Wetlands are valuable natural resources that provide high biological diversity. They filter and transform nutrients and pollutants and act to buffer the impacts of human activities on downstream aquatic systems (Hook 1993, 2157, 2160). Wetlands have been transformed in West Africa’s Upper Guinea Coast since c. 1500 CE (Fields-Black 2008, 135–160) and in North America since the 1720s to grow rice as a staple and commodity crop. In North America, the modification of wetlands continued into the 1920s (Heyward 1993, x, xxii–xxx, xxxiii–xxxiv, liii–liv, 14, 33–34, 45, 48, 50, 54, 56, 60, 62, 63–65, 67–69, 74–75, 81–82, 90, 213–216, 39). During this period, some 234,354 acres of wetlands in South Carolina were modified for rice production (Hanks et al. 2021, 7) (Fig. 2). Historic rice fields provide an interesting case study of the various forms of resilience and sustainability within the theoretical framework of alternate stable states.

Fig. 2
figure 2

Historic rice fields of the coastal plains of the southeastern U.S.A. extend from southeastern North Carolina to northeastern Florida. In green are the results of a mapping project using high resolution LiDAR to identify the historic rice fields of South Carolina

Full size image

Wetland clearing, tree stump removal, land leveling, and construction of water retention devices resulted in the first foray in the coastal plains of southeastern North Carolina to northeastern Florida, U.S.A. into the culture of rice as a staple crop to be followed with its use as a commodity crop. Ecosystems over extensive areas were substantially transformed by the rice economy and altered soils, vegetation, and hydrologies present invaluable opportunities for habitat conservation, specifically for economically important and migratory waterfowl. Queen Rice also provides important insights into resilience, in that ongoing and ecological and human dynamics produce new and invaluable stable states despite previous collapses.

The Queen Rice economy was entirely dependent on enslaved people to help planters identify microenvironments where rice could be successfully cultivated and perform the arduous labor of converting coastal plain marshes and forests to rice agriculture from the late 1600s to mid-1800s. Enslaved laborers levelled the primeval forest, felling cypress trees with axes–trunks of the largest cypress trees measured up to 12 ft in circumference–and deracinated the cypress knees with hand tools (Harper 1998, 59). Enslaved laborers made the earth as “level as a billiard table” with shovels, baskets, and planks of wood and moved 500,000 cubic feet of river muck per mile on South Carolina’s Cooper River alone to construct the hydraulic irrigation system (Rosengarten 1998, 40; Ferguson 1992, 147). Then, enslaved laborers cultivated, harvested, and processed the rice crops and maintained the hydraulic irrigation system. American and European slave traders imported an estimated 198,314 Africa captives into South Carolina and Georgia colonies between 1701 and 1858 (www.slavevoyages.com). It is likely that the majority of these enslaved people were forced to labor in the swamps on Lowcounty South Carolina and Georgia rice plantations. South Carolina rice planters and congressmen led the legislative lobby to keep the trans-Atlantic slave trade open and legal. The Compromise of 1796 resulted in the abolition of the trans-Atlantic slave trade in US colonies in 1808. The illegeal slave trade continued into the Lowcountry. South Carolina and Georgia’s share of slave importation equalled more than half (53%) of the entire number of African captives imported into the US mainland. (www.slavevoyages.com). Dependence on an unfree and unpaid labor system set up a social system and an economic system, a plantation economy, which were not resilient.

The earliest rice culture was not resilient. It used low-lying, inland freshwater environments, valley bottoms of cypress-hardwood streams, and wetlands at the heads of creeks and rivers. Colonial naturalist Mark Catesby described the land that planters converted as “impregnated by the washings from the higher lands” over a period of years to become “deep soyl [sic]…a sandy loam of a dark brown colour” (Catesby 1771, iii). Early planters adapted rice cultivation techniques to the Lowcountry environment. Inland, freshwater swamp rice plantations depended on the natural features of watersheds to better irrigate rice fields. By hand, enslaved laborers cleared hardwood forests of cypress, tupelo, and sweet gum trees, exposing soils with slow water permeability and high water-holding capacity into which rice was sowed.

The fields were located on low-lying nearly level terrain with very slight downward-sloping grades (0–2%) that allowed drainage of freshwater into the rice fields. Locations of rice fields were chosen to take advantage of water from higher elevations flowing down into the fields from surface and groundwater sources (Smith 2019, 3–6, 7–8, 29–35, 38, 96–97, 109–112, 116–118, 120–121). Enslaved laborers built clayey embankments that retained water in reservoirs and quarter-drains then released it.

The 1700s saw demand and market share for rice from the Carolinas increase and concurrently, the development of more effective technologies and infrastructures for managing water. By 1710, rice had become South Carolina’s most successfully cultivated staple crop and by the 1730s demand for rice exports was exploding. Annual exports from Charleston harbor increased five-fold between 1720 to 1740, from about 6 to 30 million pounds (Coclanis 1989, 83). Growth in the 1730s is partly attributed to the relaxation of the British Navigation Acts, enabling Carolina planters to export rice directly to Southern Europe on British ships.

Planters in the early eighteenth century were focused on economic growth. But, with increased demand and market share, planters established greater management control over the flow of water into the rice fields by constructing a complex of irrigation channels, trunks, and gates. Early trunks consisted of hollowed out tree trunks with plugs on each end. The irrigation resembled technologies used in West Africa’s rice-growing region (Carney 1996, 27; Doar 1970, 12). Planters further mechanized water control systems with valves, rectangular boxes that were open to incoming water on one end, and sliding gates to trap and release freshwater into the rice fields. Simultaneously, the valves resembled technologies English farmers were using to drain fens (Edelson 2006, 6, 34, 48, 73–74, 76, 197).

Despite technological improvements, inland rice cultivation presented serious limits to the agricultural system’s potential for growth. Planters were limited by the unidirectional flow of stream and river water, and gestating rice was vulnerable to both droughts and floods. Subtropical storm runoff readily breached the earthen embankments and washed out inland rice fields. On the other hand, the burgeoning rice export trade demanded more efficient, reliable, and predictable irrigation systems that would give planters more control over water.

South Carolina rice planter, Nathaniel Hayward’s, primary inheritance was an inland rice fields on a tributary of the Broad River in Beaufort County, South Carolina and tidal rice fields only partially reclaimed near the Combahee River. He made a good faith effort planting the inland rice fields, which took advantage of water on higher elevations in the marsh where evergreen loblolly pine and oak trees grew in dry, sandy, clay soils without altering the environment. Nathaniel Heyward planted his inland rice fields for only one season. When the rice was still in the fields and almost ready to be harvested, a “freshet” destroyed the entire crop. Legend has it that he drove out to his inland rice field in his buggy the next morning after the storm to survey the damage. His fine rice crop was submerged. Heyward took one look at the water covering it, got back in the buggy, and never went back to or planted the inland rice field again. From this point, he focused on managing his brothers’ inheritances, draining the swamps on his partially reclaimed tidal ride fields and his brothers’ larger tidal rice fields, and subsequently acquiring and building his own empire, 17 “gold mines,” tidal rice fields on the Combahee River in South Carolina’s Colleton County (Heyward 1993, 11–12, 14, 50, 65–67).

Inland rice culture provided means to store water in reserve systems as a way to provide some mitigation against unpredictable water supply, which was the primary threat to a successful crop (Smith 2019, 3, 9, 81–82, 88, 99, 195; Coclanis 1989, 78–83). There remained some uncertainty for successful crop production depending on the severity of the drought where upstream reserves could not store enough water to supply the downstream rice field. It was not until the development of the tidal field system that large scale and consistent rice crops could be produced and shipped to market. Unlike Nathaniel Heyward, not all rice planters gave up inland rice cultivation entirely. Middling planters who were not uber-wealthy like the Heywards, continued to grow inland rice primarily for subsistence. After the collapse of the Queen Rice economy in the early twentieth century, African American farmers on heirs’ property, property owned by the descendants of landowners who died intestate, well into the twentieth century (Heyward 1993, xiii–xiv; Hilliard 1975, 57–58; Merrens 1972, 187, 192; Smith 2019, 3, 9, 81–82, 88, 99, 195; Vernon 1993, 248, n.9, 274 n.7).

Inland swamp rice production was not perfect. It did not allow planters to control water and often led to too much water, in torrential deluges called freshets, or too little water in the rice fields. Perfecting water control would require more technology, more labor, even more knowledge of the coastal wetlands, and much more capital to reclaim the swamps and establish tidal rice production. It would take another few decades for all of these factors to come together in the mid-eighteenth century.

Tidal rice plantations were based on a simple principle of water control; they used the fresh water in river estuaries, which rose and fell with the tides, to flood rice fields. Tidal rice fields are located in an inland zone that is close enough to the coast to experience tidal fluctuations but far enough upstream to be freshwater. This geographic location allowed them to take advantage of the predictable tidal fluctuations and the associated freshwater wedge, thereby allowing the management of freshwater into and out of the fields.

Tidal rice plantations used water-control structures to inundate fields with the freshwater of estuaries that floated on top of the salt water and that rose and fell with the tides. With predictable environmental conditions (i.e., predictable supply of freshwater) ensured, the physical structure of the former wetlands as tidal rice fields became engineered and managed. As the process of rice culture in tidal fields was fine tuned and overall yield per acre increased, the tidal fields system was focused on a singularly objective, the production of rice for its market value. The immensity of the change to the structure and function of the wetlands across such a large geography resulted in a state shift from natural wetlands to engineered and managed wetlands, or rice fields. This combination made for the only naturally irrigated soils in the US. When management control was established over the hydrology of tidal wetlands, the area of rice cultivation greatly expanded.

Planters and enslaved laborers selected level land along rivers with tidal estuaries, impacted by the tides, accessing freshwater on either side. Planters and enslaved laborers converted level floodplains and swamplands along tidal rivers to rice fields, managing both fresh- and saltwater. Canals with floodgates were even constructed to channel freshwater from tidal estuaries to remote rice fields.

Slave labor was used throughout the time where the methodology of growing rice in the southern coastal plains of the United States was fine-tuned and increasingly focused on the tidal rice system. This societal stable state allowed forced and enslaved labor to transform a vast geography of wetlands across these coastal plains (more than 234, 354 acres in South Carolina, USA alone) (Hanks et. al. 2021, 7). Enslaved laborers converted tidal swamps to rice fields with water control infrastructures by building ditches and embankments around an entire floodplain. Next, they cleared, burned, and removed trees and stumps. Embankments that surrounded fields had wooden “trunks” installed for flooding and drainage. Trunks passed through the dikes and allowed movement between rice fields or between a tidal rice field and the tidal river. Initially, cypress trunks were used after being hollowed from top to bottom and installing a large plug to control water flow. Trunks eventually evolved into sophisticated wooden structures with gates at each end that opened and shut depending on the tide. Individual fields had cross ditches and channels excavated and check banks installed for highly precise water level control (Fig. 3). In the final stage, enslaved laborers planted rice on the floodplains.

Fig. 3
figure 3

Comparison and description of inland (a) and tidal rice field (b) morphology. Inland fields are linear, gravity fed wetlands. Widths of these wetlands can range from over 1000’ wide to just 100’ wide. Inland fields are bordered by uplands. Tidal fields were constructed in floodplain areas between sections of tidal, freshwater rivers and uplands. Inland fields tend to be narrow and long which result in smaller acreage impoundments. Tidal fields are not as constrained by adjacent uplands and individual impoundments on the average are larger acreages than those in inland rice fields

Full size image

Conversion of a tidal swamp was a “great undertaking,” one considerably more difficult than that of the inland swamps. It required significant engineering knowledge and knowledge of the natural landscape, as well as intensive capital and enslaved labor inputs over many years. In addition to clearing and leveling the land, constructing the hydraulic irrigation system, enslaved laborers maintained the irrigation system against the threat of breaks in the embankments and the rush of water. Because of the capital, labor, and time demands of tidal rice culture, only wealthy planters with multiple investments like Nathaniel Heyward, not small farmers, could undertake swamp reclamation. Then, they reinvested profits from one tidal rice plantation into acquiring more labor and reclaiming more tidal lands. The intensification of capital in the new American economy was vital to tidal rice culture (Heyward 1993, 18). By the mid-eighteenth century, tidal rice culture was extensive. By 1770, rice exports exceeded 60 million pounds per year (Fig. 1), largely due to tidal rice cultivation (Coclanis 1989, 83).

The system of slave labor became entangled with the environmental system of engineered and managed rice fields so intensively that the environmental system of engineered and managed rice fields could not exist were it not for the social system. With the environmental system of rice production now being stable and consistent (i.e., in an alternate stable state) across such a large geography and the singular focus of the rice fields being to produce marketable rice, slave labor became an integral cog in the socio-environmental system of rice culture in the southeastern United States. In other words, to maintain the stability of the environmental system (i.e., rice fields) required the stability of the social system where slave labor was foundational.

The full tragedy of Queen Rice is that African–Americans were at high risk of disease and survival rates were notably low in New World rice plantations. Though yields of tidal rice were incredibly productive and financially lucrative and though enslaved laborers contributed labor as well as critical skills, tidal rice culture came at a high cost for enslaved laborers. The saturated and inundated environments of the inland and tidal rice fields were extremely unhealthy environments. Rice plantations in the South Carolina and Georgia lowcountry had among the highest death rates among enslaved children and adults in the US, and second only to sugar plantations in the entire New World (Forster and Smith 2011, 909, 923). Whereas death rates for slaves on cotton and tobacco plantations dropped to approximately 33% by the 1780s, double the number, approximately two-thirds, of enslaved people still died on lowcountry rice plantations up until the Civil War. Along the Savannah River, 90% of children enslaved on rice plantations died before 15 years of age. In the winter of 1839 when most of the children died on Pierce Butler’s Butler Island rice plantation on the Altamaha River near Darien, GA, the mother of a child who recently died described the plight of many women enslaved on Lowcountry rice plantations saying over and over again to Fannie Kemble, Butler’s English wife: “I’ve lost a many; they all goes so” (Dusinberre 1996, 2–3, 49–51, 55–56, 58, 61, 74, 80–81, 84, 103, 121, 188, 199, 237–238, 240–241, 245, 325, 412–413, 415–416; Kemble 1984, 130).

The tight coupling of the social and environmental systems in the production of rice as a commodity crop through the engineered tidal field system operated within an engineering resilience framework. Production of rice for market value was the single objective of the tidal rice field system and any alternate state, for either the environmental or social system, was potentially not acknowledged but certainly to be avoided at all costs. Maintaining the system in an engineering resilient framework required constant input of energy which was provided by slave labor. Southern planters were unable to assess potential risks to the coupled socio-environmental system they had developed and fostered because they were operating in an engineering resiliency state-of-mind, where no other potential alternate stable states were envisaged. In this framework, the environmental stability of the tidal rice fields was a requisite that had to be maintained to produce rice and the only way this was possible was through slave labor.

The external forces that tested the resilience of the environmental system (i.e., engineered and managed tidal rice fields) still existed in both chronic (e.g., the erosion of dikes along riverbanks) and episodic (e.g., hurricanes) but this was overcome with the immense human power of forced free labor provided by a social system that enabled slave labor. Any threats to the social system (i.e., slavery) was quashed by the system itself. That is until the American Civil War put an end to slavery. At this point, both environmental and social systems underwent interlinked perturbations that allowed both to realize various trajectories previously unacknowledged and likely beyond contemporaneous comprehension. People who were once enslaved were now “free” and those who enslaved them now had to envision new ways to manage their engineered rice fields without slave labor. This resulted in a period after the American Civil War where planters attempted to continue to produce and manage rice as a commodity crop within the engineered rice fields up until the last commercial rice crop in South Carolina was produced by ss. In Fig. 1 this is represented by the small (and temporary) alternate stable state (termed “transition era”), which was fragile at best, requiring only small perturbations to push the system into a completely different stable state. These perturbations came in the form of several hurricanes and disruptions in market supply chains that affected planters in the southeastern coastal plains.

This transition era reflects the point made in Haldon et al. (2020, 1) that systems seldom collapse in the dramatic fashion so often popularized in modern culture. The rice culture that began in the 1670s and saw its ultimate demise beginning just prior to the American Civil War did not change the social nor the environmental systems in rapid fashion. Still today American society struggles with racism, some 155 years after the end of the American Civil War. The environmental system continues to change and may require more time to reach the stable bottom of the cup than that of the social system.

The postbellum social system disrupted the production of rice as a commodity crop in the southeastern U.S. due to the abolishment of slavery, but it also affected the engineered rice fields where, after some time, it was no longer seen as a tenable option to manage for rice production. These managed wetlands now experienced various ecological trajectories. While some previously managed fields were unmanaged and allowed to “re-wild,” still others were managed for another objective–waterfowl hunting. The utilization of rice fields for waterfowl hunting beginning in the 1910 and 1920s has continued to evolve as a conservation ethic has percolated through this region. In recent years management of engineered tidal rice fields has become more diverse in the set of objectives that now includes, along with waterfowl, ecosystem services such as wildlife habitat (e.g., black rail, wood storks, roseate spoonbill, American alligator, etc.). These “new” objectives and their socio-environmental stable states are represented by the third cup in Fig. 1 and have yet to be fully established.

Resilience, Climate Change, and the 21st Century Rice Field Infrastructure

Given that the rice fields in South Carolina have significant historical, cultural and ecological significance, it is prudent to consider the permanence of these man made systems. Over the course of rice history in South Carolina, there have been several shifts in locations and objectives of rice fields. Initially the potential to reap financial profits started the rice economy in South Carolina and planters developed and used the inland field system. Ultimately tidal rice fields provided a financially successful alternative to inland fields and planters shifted their development and management in this area. These tidal fields (and inland fields to a lesser degree) transitioned from a financial to an ecological objective with the end of rice as a commodity crop and the rise of sporting pursuits on the rice plantations. From the early twentieth century this ecological objective has persisted and become more diverse with recognition that the management of these tidal and inland rice fields benefits waterfowl and many other non-game species like bald eagles, wood storks, black rails, etc.

There is increasing awareness by the owners and managers of the rice fields that the permanence of the existing system is being influenced negatively. Federal, state, and private owners of rice fields are faced with changing forces on this infrastructure. Decision making about how, when and how much to invest in these man-made systems is complex and has been ongoing since their creation.

Rice fields are composed of raised dikes that prevent water from entering or exiting a particular area where rice was grown and now is managed for wildlife habitat (Fig. 3). Canals were excavated to enable water flow throughout the system. Water control structures were placed in dikes to permit water retention or dewatering in these rice fields. Other than the water control structures (which are typically wooden), this system is constructed from onsite mud and soil. The properties of this mud and soil have influenced the maintenance regimes of the earthen infrastructure from the very inception of rice field construction in the early eighteenth century. As an example, some plantations may have been established along sections of rivers where the local material had a high sand content. Other rice fields were established along particular rivers where the available soil material was higher in loam or clay. When building dikes that stand 4–6’ above the wetland grade, soils with higher clay content are able to persist longer with the normal erosion forces of rain, travel across the dikes, etc. These constant erosion forces require these dikes to have material placed back on top and the interim period between these efforts can vary from 5 to 10 years for areas of sand versus 10–15 years for areas of material with higher clay content.

Rice planters initially and wildlife habitat managers today have dealt with this constant degradation of the built rice field system. Retopping dikes, installing new water control structures, excavating canals for improved water circulation were all acts that have been required from the very beginning of rice culture and were incorporated into the mental calculus of determining whether it was worth the financial investment to perform these remedial acts. Maintenance and repair issues have always been a part of the rice field landscape and until recent decades were costs nearly all were willing to bear to maintain the system.

The costs and efforts, though, of maintaining rice fields, especially tidal ones, has become more costly and more frequent in recent decades. Environmental forces that have been influenced by climate change are causing increased degradation and loss of the rice field infrastructure. These forces include increases in tidal amplitude as driven by sea level rise and increase in the frequency of tropical storm events as a result of climate change. We discuss each of these factors below and how they negatively impact rice field infrastructure.

Tidal rice fields were placed along the tidal rivers in creeks to take advantage of the tidal, freshwater. Dikes and water control structures allowed the intentional flooding and dewatering of the rice fields depending on different times of the rice growing season. Since the transition to management of wildlife habitat, the intentional flooding and dewatering of the tidal rice fields enables management for native plant communities (e.g., widgeongrass in brackish and smartweed and panic grasses in freshwater rice fields) that do not develop under normal tidal regimes in free tidal flow marshes.

At a mechanistic level, tidal fields worked because the dike heights were built to a grade above mean high water. The bed of the rice field (i.e., the broad acreage where rice initially and not native plants were and are grown) was at a level above mean low water (Fig. 4). This enabled full dewatering of the rice field because as the tidal river reached low tide, i.e. below the bed level, water from the tidal rice field passed through water control structures from the rice field and into the free tidal flow water bodies.

Fig. 4
figure 4

Cross section sketch of a tidal rice field bed, canal and perimeter and dike. Tidal amplitudes during the era of rice field development (i.e., late 1700s until mid 1800s). MLW level is at a point below the rice field bed such that water could easily pass from the tidal rice field into the tidal rivers. Sea level rise in the late twentieth and current twenty-first century have shifted this tidal amplitude up such that MLW levels are just below or at bed level and thereby making it difficult to fully dewater tidal rice fields for wildlife habitat management objectives

Full size image

Sea level rise impacts are most visible in coastal communities. The impacts of more frequent flooding on tourist and beach communities are commonly reported in the media (Tibbetts and Mooney 2018; Cappucci 2020). Additionally, sea level rise also influences tidal amplitude inland along tidal rivers. In South Carolina, these river systems are typified by the Combahee, Ashepoo, Edisto and Santee Rivers. Coastal South Carolina has seen a significant increase in tide levels. Since 1950, tidal waters have increased 10 inches in Charleston, which is central along the coast to rice growing areas of SC (Anonymous 2019, 6). Additionally, this increase appears to be increasing to a point where tidal increases of 1 inch every 2 years is anticipated.

These dramatic statistics within the tidal rice field landscape are forcing landowners to think of how increasing mean high water marks interact with the grade of perimeter dikes. Indeed, increasing numbers of spring tides, i.e. the strongest tide of the lunar cycle, are now overtopping these perimeter dikes. Efforts to raise them are ongoing on rice plantations. In fact, because of the increasing mean high water, efforts to raise dike levels over the last decade are ongoing in all areas of tidal rice fields across South Carolina.

However, there is another more difficult dynamic associated with the increased tidal amplitude. Increasingly managers of tidal rice fields have difficulty fully dewatering the fields during low tide periods because the mean low water mark has also increased over time. Thus, the time and potential of water to pass from the tidal rice field and into the tidal river is limited. Because these tidal fields are managed for wildlife habitat and because many of the native plants require periods of drying to the bed, the management focus for wildlife is becoming more difficult. Some plantations have installed mechanical pumping stations to ameliorate the impact of increasing mean low water marks, but this cost is additive to the cost of dike maintenance and retopping.

Climate change has also impacted the frequency of tropical storm events (Marsooli et al. 2019, 5). Coastal South Carolina has seen these impacts recently with nine tropical storms events impacting coastal South Carolina since 2016 (Mizzell et al. 2020, 12). Luckily, there is a trend for the increased tropical storm events to be storms with less intensity than in the past; however, these events lead to excessive flooding from rainfall and tidal surge. Both sources of excess water in tidal rivers cause excessive dike erosion, dike breaching, and loss of water control structures. In recent years, some plantations have performed these dike repairs between hurricane seasons only to be forced into the same repair the next year caused by another storm.

Tidal rice fields are more susceptible to these impacts than inland fields for two reasons. First, tidal fields are directly adjacent to tidal rivers and creeks. Therefore they are immediately impacted by increases in tidal amplitude and storm surge as a result of tropical storm events. In contrast, inland fields are insulated by geography from these impacts; however, intense rain events can cause excessive flooding through the system, which degrades dikes and water control structures. In general, the cost of maintenance of tidal fields versus inland fields is 1.5–2 times higher (per acre of managed wetland). One complicating factor though is that more tidal fields than inland fields are still actively maintained and managed for wildlife habitat.

There are few absolutes when dealing with environmental forces. One is that man is rarely successful in engineering solutions that will completely ameliorate the impacts on an anthropogenic landscape. So why then do owners and managers of tidal rice fields continue to repair and maintain these systems in the face of increasing pressures? What are the alternatives to the tidal rice field system for wildlife habitat management? What are the societal forces that would entrain owners and managers to continue to repair tidal rice fields versus move back to inland fields where restoring dikes, canals, and water control structures is easier and less costly per acre? All of these questions are being considered informally across the coast of South Carolina.

Historically, real estate values have been the motivators for persistence in maintaining and repairing tidal fields through the recent impacts of increases in tidal amplitude and storm frequency. Tidal rice fields, when well managed for wildlife, can be valued at $8000 to $10,000 per acre. These values are significant when considering some tidal fields are hundreds of acres. The value of tidal fields where the dikes not intact and management not possible would diminish to approximately $250 per acre. Furthermore, the overall real estate of many of these plantations exists because of the presence of functional tidal rice fields on the property. Would land owners be willing to pay these prices if the tidal fields were not functional (i.e., dikes are breached, water control structures are not present)?

The attractiveness of the habitat to wildlife itself must also be considered in the question of tidal versus inland rice fields. In general, many water birds (waterfowl and other species) typically do not use the area of habitat in close proximity to the dike infrastructure. There is a band that surrounds these dikes where the habitat may be suitable, but wildlife do not use it with as great a frequency as the interior of these wetland units. This dynamic has not received much research, but it is hypothesized that water birds avoid dikes due to the disturbance of travel across the dikes.

Many acres are still accessible to water birds in a squarish-configuration of hundreds of acres of tidal rice fields. This is in contrast to inland fields that tend to be narrow and long. Might many inland fields be too narrow to allow full habitat utilization by wildlife without the hypothesized perimeter disturbance effect? Research on this has not been conducted but would be useful in better understanding how transitioning financial and logistical resources away from tidal and into inland fields might succeed.

Conclusion

Change is certain, whether it be social or ecological and often the two co-mingle and affect one another. Unlike the white rice field planters of the antebellum southern U.S., who were unable to envisage any other stable state, contemporary society must attempt to project future changes and evaluate mitigating solutions to possible risks. Historic rice fields, as a social-environmental system, are facing multiple changes due to climate change. As such, they are a prime case for evaluating society’s ability to consider alternative scenarios where current social and environmental functions may change but large scale changes, or even functional loss, may be ameliorated. In this light, many stakeholder groups who are part invested in the socio-environmental system of historic rice fields are confronted with deciding how and if they should deal with increased sea levels and tropical storm activity. Understanding the magnitude of impacts and the nature of the resource lost to climate change is a wise first step in evaluating the type of mitigating response.

In the case of rice fields, we know their historical significance, their place in the cultural fabric of coastal South Carolina, and their importance as valuable wildlife habitat. How can these components of historic rice fields, or potentially a subset of these components, be maintained given the impending threats? Several questions come to mind: (1) What, of the socio-environmental attributes of the rice fields, should be the focus of conservation efforts?, (2) What are the possible implications of conserving one attribute while forgoing conserving another (i.e., what does a new alternate stable state look like?), (3) Who decides what attribute(s) to conserve?, (4) What effect will possible changes in the environmental system have on the social system and vice-versa?, (5) What potential means are available to achieve conservation of the decided upon attributes to be conserved? These are not easy questions to answer given the complexity of either the social or environmental systems as separate entities, let alone when attempting to consider them as a single co-mingled and interacting system.

As a hypothetical example, it may be possible to shift the ecological function of the threatened tidal fields (due to sea level rise and increased tropical storm activity) to inland fields. In this example, inland fields could be cleared of timber, tree trunks removed, the land leveled, and water retention and control structures and devices installed to reclaim the forested land to its former rice field structure. As the structure of tidal fields changes and presumably functional loss occurs, the hope would be for these reclaimed inland fields to take on the structure and function of tidal rice fields. If this were to be successful, it would increase the resilience of the ecological system; however, there are likely cascading effects to the social system that must be considered. The loss of structure and function of the tidal fields, where the primary focus is on waterfowl hunting and their contemporary maintenance is provided by a relatively small group of landowners, will likely result in changes in the structure of monetary support for conservation efforts in the region. In other words, the structure and function of today’s tidal fields and the resulting large scale conservation activities are primarily maintained by a small group of landowners. Without the available environmental structure to support waterfowl hunting, these landowners may forgo financial support for conservation across the region. Shifting the ecological structure and function of the tidal fields to the reclaimed inland fields will result in a different spatial arrangement and potentially different land ownership of these landscape features. The owners of these newly reclaimed rice fields may have a different conservation ethic than the owners of the “lost” tidal fields. What might this mean for the ecological structure and function? How might this impact the societal system within the region?

With inevitable change to both environmental and societal systems, some of which is foreseeable while others may not be, society should consider what the value of the various attributes of any given social-environmental system are, what maintains the system’s structure and function, what are the possible threats, however likely, to the various attributes of the system, and what the structure and function of alternate stable states might be. Such efforts should provide various scenarios where the resilience of socio-environmental systems is increased. In doing so, society will hopefully be able to promote wise use of environmental resources that meet the needs of both contemporary and future societies.