Martínez, M.L.; Taramelli, A., and Silva, R., 2017. Resistance and resilience: Facing the multidimensional challenges in coastal areas. In: Martinez, M.L.; Taramelli, A., and Silva, R. (eds.), Coastal Resilience: Exploring the Many Challenges from Different Viewpoints. Journal of Coastal Research, Special Issue No. 77, pp. 1–6. Coconut Creek (Florida), ISSN 0749-0208.
Coastal ecosystems are subject to recurrent natural disturbances that act as drivers of ecosystem dynamics. In addition, in recent years, human impact has exerted intense pressures on these ecosystems, altering the dynamics and reducing resistance and resilience. The former refers to the ability of a system to hold a force without any modification, while the latter is a measure of its the capacity to respond to the consequences of perturbation and return to its original status. How can we achieve coastal management actions so that coastal resistance and resilience are enhanced? This volume integrates a broad set of studies that analyse coastal resistance and resilience from different viewpoints, that include contrasting viewpoints that cover the natural environment (abiotic and biotic); social governance and networks; social dynamics; built infrastructure and a combination of the four. Indeed, a proper diagnosis of the status of the coast is required and adequate coastal management is necessary, so that risks to the population and environmental problems are minimized. Coastal managers, ecologists, engineers, decision makers and society in general are jointly responsible for the future of our dynamic coasts.
Coastal regions are heterogeneous, dynamic and complex systems with a wide variety of landforms, ecosystems and processes. They are exposed to recurrent extreme disturbance events which can be natural (e.g., flooding, storm impact, erosion) or anthropogenic (e.g., sea-level rise, exacerbated erosion and acidification). On top of this, human settlements and socio-economic activities are increasing, as human populations grow in these low elevation coastal zones (McGranahan, Balk, and Anderson, 2007). In fact, it is estimated that 21% of the world population live within coastal zones (Simonovic and Peck, 2013) and 10% live at less than 10 m above sea level (McGranahan, Balk, and Anderson, 2007). This means that about 10 million people experience flooding each year (Nicholls, 2004) and nearly 189 million people live below the one-in-a-hundred-years high storm surge level (Heilig, 2012; Simonovic and Peck, 2013). Furthermore, as sea level rises and coastal urbanization advances, the phenomenon called “coastal squeeze” becomes more frequent (Doody, 2004; Pontee, 2013). The result of the combination of these factors is an increasingly degraded and altered coastal environment with a growing population and infrastructure at risk. One example of this is the exacerbated erosion that is occurring on most coasts (Silva et al., 2014).
Given the increasing range of environmental and socio-economic pressures, it has been suggested that promoting coastal resistance and resilience can reduce vulnerability (and thus lessen the risks for the population and built infrastructure) and be effective in dealing with the unpredictable changes on the coast (Guannel et al., 2016; Rosati, Touzinsky, and Lillycrop, 2015; Simonovic and Peck, 2013). In order to enhance resistance and resiliance we need to understand better the interdependence between human populations and natural ecosystems.
Coastal resistance refers to the ability of a system to hold a force without any modification, while coastal resilience is a measure of the system's capacity to respond to the consequences of perturbation (Klein and Nicholls, 1999). Thus, resistance is the capacity exerted before the system is perturbed, while resilience can be measured when the perturbation has occurred. Human activities often reduce or modify both. Studies on coastal resistance do not abound in the literature, and they are mostly focused on ecological processes. For instance, Andersen (1995) tested the impact of the disturbance generated from human trampling on different coastal vegetation types, and found that coastal dunes were the least resistant while saltmarshes were the most. Other studies have focused on community resistance to species invasions. For example, Stachowicz, Whitlach, and Osman (1999) observed that declining diversity facilitated species invasions in experimental communities of sessile marine invertebrates. Similarly, Thomsen et al. (2006) reported that seed density and moisture conditions determined the ecological resistance to invasions by plant species. Resistance to eutrophication in water bodies were also tested (i.e. Lloret and Marin, 2009). In the first study it was shown that hydrodynamic mixing modified abiotic conditions (including nutrient losses) which limited primary production and induced stability (and hence resistance) in the phytoplankton community. Similarly, Lloret and Marin (2009) confirmed that benthic macrophytes removed excess nutrients from the water column by storing them in the sediments, thereby enhancing the resistance to eutrophication.
Few studies have explored the resistance capacities of natural ecosystems and their role in coastal protection. Mazda et al. (1997) tested how mangrove forests provided protection through a reduction in wave flow. Houwman and van Rijn (1999) describe how flow resistance was affected by bed roughness and Kadlec (1999) modelled vegetation resistance to overland flow in wetlands. The combination of numerical models and field observations performed by Harada and Imamura (2005) showed that mangrove forests provide protection from tsunamis: an increase in the width of mangrove forest can reduce inundation depth as well as current and hydraulic force behind the forest. Finally, the wave flume experiments performed by Silva et al. (2016) confirmed that vegetation helps prevent beach and dune erosion.
In contrast, the term “coastal resilience” has been used for several decades (Holling, 1973; Manyena, 2006; Timmerman, 1981). Here, resilience is considered as the “capacity of linked social-ecological systems to absorb recurrent disturbances and retain the essential structures, processes, and feedbacks” (Carpenter et al., 2001; Holling, 1973; Walker et al., 2004). The resilience of a system indicates the degree to which it is capable of recovering its dynamic equilibrium. When the self-reinforcing feedbacks are over-powered by extreme disturbances, the feedbacks promote alternative states. That is, under extreme conditions the system is pushed beyond a threshold and it cannot return to the original state but shifts to an alternative one (Jiang, Gao, and DeAngelis, 2012). Consequently, resilience is considered a desirable attribute in the face of short (resource depletion, pollution, urbanization) and long term pressures (sea-level rise and climate change) (Klein et al., 1998).
Resilience is not easy to assess, because the conditions that define it change with spatial and temporal scales. For example, Alongi (2008) and Woodroffe (2007) mentioned that coral reefs and mangroves, respectively, appear to be resilient given their persistence in the geological record. However, in contrast with this robustness, they also seem fragile and sensitive to local environmental changes. Resilience is also affected by the interactions between trophic levels, as was shown by Watson and Estes (2011), who observed multiple equilibrium states that determined resilience in rocky subtidal communities. Also, short-term and low-scale environmental changes have a different impact on community resilience in seagrasses (Carlson et al., 2010). Here, seagrasses were more resilient when exposed to hurricanes than to other environmental changes such as suspended sediments, phytoplankton blooms and dissolved organic matter.
Socio-ecological resilience is also difficult to determine, because a society may be considered resilient to environmental hazards; e.g., to short-term phenomena, such as severe weather due to mitigation measures that have been adopted, but not to long-term environmental hazards, such as climate change. In the last decade, many recent studies have focused on socio-ecological resilience to disasters (Adger et al., 2005; Balica, Wright, and van der Meulen, 2012; Hoggart et al., 2014; Rosati, Touzinsky, and Lillycrop, 2015; Simonovic and Peck, 2013) and management schemes include actions to increase resilience (Ladd and Collado-Vides, 2013). Disaster resilience has been acknowledged in the scientific literature for more than 30 years (Paton, Smith, and Violanti, 2000; Torry, 1979), but it was only brought to the attention of governments in 2005, after The Hyogo Framework of Action adopted by the United Nations. It is now recognized that socio-ecological resilience to natural hazards or other disturbances largely relies on ecosystem resilience (Bridges et al., 2014; Rosati, Touzinsky, and Lillycrop, 2015; Sudmeier-Rieux and Ash, 2009; Taramelli et al., 2014). For example, Hoggart et al. (2014) found an increased resilience to floods in species-rich communities, while (Ladd and Collado-Vides, 2013) dealt with management actions that can increase the resilience of ecosystems.
All in all, the mechanisms that support coastal resistance and resilience, which are linked to the biophysical system and a range of properties that include social and economic components, remain largely unknown. Nevertheless, it is clear that the dynamic nature of the coast and how humans relate to it must be taken into account (Martínez et al., 2006). This is relevant in order to clarify the actions that are necessary to incorporate resistance and resilience into coastal management decisions. In this sense, Klein et al. (1998) recommended three possible approaches that are still valid: a) to consider the effects of increasing morphological and ecological resistance and resilience on socio-economic interests; b) to analyse the constraints that socio-economic interests force on ecological and morphological resistance and resilience; and c) to estimate the accountability of the social costs of compensating losses in morphological and ecological resilience. The inclusion of resistance and resilience in management decisions requires the knowledge of how the physical environment (natural and built), social dynamics and governance networks overlap and interact (Figure 1). Indeed, the balance and interactions of these areas, combined with an increasing awareness of the consequences of different decisions, will help humans to live with, rather than cope with, our dynamic coasts (Pérez-Maqueo, Intralawan, and Martínez, 2007). When we live with Nature we are adapted to the natural dynamics, while when we cope with Nature we force the system towards our pre-conceived status, which is a non-existent stability in the case of the coast.
This volume integrates a broad set of studies that analyse coastal resistance and resilience from different viewpoints, with the idea of exploring how this perspective can be incorporated into management decisions. Our starting point in this issue was that the dynamics of coastal dunes, wetlands, water bodies and the shore, coupled with urbanization, can be used as a measure of stability resulting from a combination of biotic and abiotic characteristics. The volume includes viewpoints that cover the physical environment (analysed in the field, through remote sensing and numerical modelling exercises); the biotic community; social governance, built infrastructure and a combination of the four areas outlined in Figure 1.
The first set of papers deal with the physical environment, and include the swash zone, an open bay, and coastal lagoons. Chávez-Cárdenas and Kobayashi (2017) performed laboratory experiments in a wave flume in which they tested how idealized houses located on the shore and berm, as well as houses on pilings, were affected by waves.
They found that floating or sliding blocks (simulating houses) were dependent upon swash hydrodynamics and clearance above the sand. This study provides evidence of how the location of infrastructure determines its resilience to extreme waves. In the same train of thought, Mendoza et al. (2017) tested how vegetation can help reduce beach erosion. Wave flume experiments and numerical models showed that vegetation retarded erosion time and thus, contributed to beach resistance and resilience. The corollary of these two studies is that, although locally effective, hard infrastructure used for coastal protection generates a rigid coast that alters shoreline dynamics, degrades ecosystem services and damages the landscape. Alternatives to this dilemma can be moving infrastructure further inland or to higher levels (Chávez-Cárdenas and Kobayashi, 2017), and restoring vegetation, which in turn will contribute to the resistance and resilience of the beach (Mendoza et al., 2017; Silva et al., 2014).
The hydrodynamics and biological, physical and chemical characteristics of water bodies (the resistance and resilience properties) can be affected by natural morphological attributes and also by human activities. This is shown in studies by Chávez et al. (2017), de la Lanza et al. (2017), and López-Portillo et al. (2017). Chávez et al. (2017) showed that the beach was resilient to the impact of winter storms as long as the sediment supply is not interrupted. In this lagoon, the natural cycles of the inlet are modified by local fishermen, who open the inlet once or twice a year to improve production. Possibly, such anthropogenic interference is affecting the resilience of the lagoon. In turn, de la Lanza et al. (2017) observed that Petacalco Bay shows worrying concentrations of phosphorous, and evidence of eutrophization associated with urban settlements and fertilizer industry, as well as the cooling system of a thermoelectric power plant having a clear effect on temperatures. Similarly, the field study of a coastal lagoons by López-Portillo et al. (2017) showed that differences in physical and chemical conditions of three coastal lagoons were possibly related to the geomorphology of each, inlet dynamics and hydrodynamics.
Coastal resilience has also been studied through numerical and analytical methods, as is presented in studies by Cappucci et al. (2017) and Taramelli et al. (2017). The research by Taramelli et al. (2017) shows how during near short-time scenarios (14, 28 and 60 days) climatic and hydrodynamic variables may influence the non-linearity of vegetation patch size frequency distribution. Their results highlighted the numerical thresholds tipping point, that can describe the possible cumulative long time-based inundation effects related to the evolution of the channel system in Northern European wetlands. The use of satellite imagery, an innovative way to investigate coastal resilience, was already used in the methodology proposed by Valentini et al. (2015). This novel algorithm and methodology in estuary and delta habitat mapping is able to assimilate the value of a priori knowledge in an automatized remote sensing processing algorithm.
The same approach is applied to detected Anthropocene features by Cappucci et al. (2017). Geologists have already defined the Anthropocene, a new geological era, when the growth in global consumerism, and many forms of social exploitation are increasing contamination and inducing changes that are detrimental even to the structure of the land and the sea surface. In Cappucci et al. (2017), seabed forms are investigated with combined airborne LiDAR and hyperspectral technologies. In Mediterranean pocket beaches, the spatial pattern of the response to shaping during the Anthropocene may be indistinguishable from patterns of natural variability. Mapping features using spatial datasets, remote sensing and recently developed analytical methodologies is a major advance in evaluating human pressure and impact.
The close interaction between the abiotic and biotic elements of coastal ecosystems clearly affects coastal resistance and resilience. This was observed in the studies by Huff and Feagin (2017a,b) and Moreno-Casasola, Hernández, and Campos C. (2017). In the first study, Huff and Feagin found that salt marsh loss and its conversion to open water were the result of disturbances in hydrological conditions, and were not associated with sea-level rise and changes in precipitation. The lack of tidal fluctuation, due to the presence of a barrier to water flow, resulted in hypersaline conditions and very high water levels, and were largely responsible for the loss of salt marshes. Based on this information, Huff and Feagin (2017b) used numerical modelling to identify the area that needed to be removed from the channel in order to restore the hydrologic flow and thereby recover the saltmarsh community. They removed 780 m3 of shell and mud debris and monitored salinity and tidal flow in order to test if these actions had restored the state of the saltmarsh prior to the presence of this barrier. Once the abiotic conditions were re-established, the community began to recover, with vegetation colonizing previously harsh (high salinity) areas and fish accessing the marsh. In contrast with the above, Moreno-Casasola, Hernández, and Campos C. (2017) showed how species composition of different wetlands is related to carbon sequestration and water retention. In this case, community structure and composition modified different environmental variables such as carbon stocks, carbon sequestration and water retention, thus confirming the role of plant diversity in ecosystem processes. This group of studies shows the close interdependence between abiotic and biotic conditions and how the system may change when these are altered.
Finally, as mentioned earlier and as shown in Figure 1, coastal resistance and resilience is a multidimensional challenge that involves not only the abiotic and biotic elements of the coast, but also the social dimension. In this sense, the last set of studies in this volume deal with the social dimension. Lithgow et al. (2017) looked for differences in the perceptions of academics and decision-makers in terms of the relationship (dependence and impact) between economic activities and ecosystem services. These authors found that the academics frequently perceived that the negative impact and dependence of economic activities on ecosystem services was much greater than that perceived by decision-makers. These differences may partly account for the inadequacy of public policies that result in increasing environmental degradation and loss of ecosystem services. In turn, Vanderlinden et al. (2017) explored the role of science-based knowledge and the knowledge gap in coastal stakeholders in terms of climate change risk mitigation and risk perception. They found that stakeholders and society as a whole perceive risk through norms and values and that science-based understanding of flooding has little impact in society. Thus, coastal risk governance under climate change needs to consider science-based knowledge as well as stakeholder values. Langle-Flores, Ocelík, and Pérez-Maqueo (2017) explored whether socio-ecological resilience can affect the decision-making process linked to ecosystem transformation and degradation. In this study, they performed a social network analysis to understand how local, regional national and international networks affected the final decision regarding a large tourist development project. That is, in this case, socio-ecological resistance and resilience stopped the development project and resulted in ecosystem conservation. Lastly, this volume ends with a paper in which Martínez et al. (2017) analysed the physical, biological and social components of the coast, to test how the interaction of the three affect coastal resilience. They found chronic erosion problems owing to subduction, rising sea-levels, a fall in the amount of sediments available and the inadequate design and construction of coastal protection infrastructure. Coupled with this, human encroachment has generated a coastal squeeze phenomenon, which is becoming increasingly relevant (Martínez et al., 2014). The points raised in this paper apply to many coasts throughout the world, showing that proper management of the coast is that which tests the responsibility of all sectors in society, including engineers, ecologists, decision-makers and society in general.
Recently, Rosati, Whitlatch, and Osman (2015) stated that coastal resilience is based on four concepts: prepare, resist, recover and adapt. These concepts are necessary to face the current status of the coasts: increasingly degraded, encroached by humans and with ecosystems, population and infrastructure increasingly at risk. The resilience of many socio-ecological systems is eroded, especially when societies are vulnerable and marginalized.
The resistance and resilience of coastal ecosystems is becoming increasingly relevant for human livelihoods, and thus, they can no longer be taken for granted. Instead, it is necessary to understand the processes that support socio-ecological resistance and resilience (Adger et al., 2005; D'Agostino, 2008; Folke et al., 2002). This knowledge must be adequately integrated into the decision-making process, and permeate social networks. Social networks are crucial to develop the social capital which in turn generates the political, legal and cultural frameworks that enhance resilience.
Given the increasing risks of coastal populations, and the very relevant role of coastal ecosystems in shoreline protection, it is very important that society is adapted to the dynamic and increasingly changing coastal environment (with adequate built infrastructure combined with well-preserved coastal ecosystems). When the coast is resilient, communities are able to recover and they can adapt to living with Nature instead of living in Nature.
We are very grateful to Charles Finkl and Chris Makowski for their support and enthusiasm during the development and production of this Special Issue. Also, thanks are due to the many reviewers who helped us guarantee the quality of the articles ensembled here.