Restoring resilience: Can restoring coasts with ecosystem-based solutions protect social-ecological systems from the impacts of climate change?Posted: May 2, 2016
By Anni Brumby
Victoria University of Wellington
The destruction of hurricane Katrina in New Orleans in 2005 (Photo 1), extreme flooding on the east coast of Australia in 2007, and last year, my local train station in Porirua completely underwater. Welcome to the stormy and wet world of global climate change.
Many of the threats caused by climate change are especially severe in coastal and low lying areas (Nicholls et al., 2007). This is a major concern, as coasts all over the planet are densely populated. Coastal areas less than 10 metres above sea level cover only 2% of the Earth’s surface, but contain 13% of the world’s urban population (McGranahan, Balk, & Anderson, 2007). Often coasts are highly modified for human purposes, and crucial for economic stability (Martínez et al., 2007).
The observed and predicted coastal hazards include sea level rise and the resulting inundation; erosion and salinization of land (Gornitz, 1991); increased precipitation intensity and run-off; and storm flooding (Nicholls & Lowe, 2004). Climate change will also increase the frequency and intensity of weather extremes, such as hurricanes (Emanuel, 2005; Seabloom, Ruggiero, Hacker, Mull, & Zarnetske, 2013).
The existence of Homo sapiens rely on ecosystem services – “the benefits people obtain from ecosystems” (Millennium Ecosystem Assessment, 2005, p. 1), such as food production, raw materials, waste treatment, disturbance and climate regulation, water supply and regulation…The list goes on. Coastal ecosystems contribute 77% of global ecosystem-services value (Martínez et al., 2007), thus any coastal threats affect have major impacts for humans both economically and socially.
It is unlikely that we can stop global warming (Peters et al., 2013), but is there any way to mitigate the risks? Even if we cannot prevent the sea levels from rising or storms raging, maybe we can protect our coastal ecosystems and cities by restoring resilience in social-ecological systems with ecosystem based defence strategies.
Concept of resilience
Resilience was first introduced as an ecological concept by Holling in 1973, the idea mainly referring to dynamic ecosystems that can persist in the face of disturbances. High ecological resilience is closely linked to high biodiversity of ecosystems (e.g. Oliver et al., 2015; Worm et al., 2006). As people are increasingly seen as an integral part of the biophysical world (Egan, Hjerpe & Abrams, 2011), our current understanding of resilience now also includes the human dimension. According to one definition, resilience is the capacity of social-ecological system to sustain a desired set of ecosystem services in the face of disturbance and ongoing evolution and change (Biggs et al., 2012, p. 423).
From human-engineered to ecosystem based defences
For a long time, coastal hazard prevention relied solely on so called “hard solutions”, such as building of sea walls and dykes (Slobbe et al., 2013). Recently there has been a shift towards “softer” approaches. These so called ecosystem-based adaptation or defence strategies aim to conserve or restore naturally resilient coastal ecosystems, such as marshes and mangroves, in order to protect human population from natural hazards (Temmerman et al., 2013). Restoring shores for protection is not a new idea, but it has gained momentum in recent years. Many volunteer groups are focused on restoring coastal ecosystems, such as the Dune Restoration Trust in New Zealand. Globally, the influential Nature Conservancy funds a project called Coastal Resilience, which aims to reduce coastal risks to communities with nature-based solutions (Coastal Resilience, 2016).
Restoring dune vegetation can help reduce erosion, while increasing and maintaining the resilience of coastal zones (Silva, Martínez, Odériz, Mendoza, & Feagin, 2016). Coastal ecosystems, for example forested wetlands and marshes, can play a significant role in reducing the influence of waves (Fig. 1) and floods (Danielsen et al., 2005; Hey & Philippi, 1995; Mitsch & Gosselink, 2000; Seabloom et al., 2013). In southeast India coastal zones with intact mangrove forests and tree shelterbelts were significantly less affected by the catastrophic Boxing Day tsunami in 2004, than the areas where coastal vegetation had been removed (Danielsen et al., 2005). Coastal vegetation can also buffer gradual phenomena such as sea-level rise or tidal changes (Feagin et al., 2009).
One of the benefits of ecosystem-based strategies compared to traditional human-engineered solutions is that they are more cost-efficient. For example, investment of US$1.1 million on mangrove restoration to protect rice fields in coastal Vietnam has been estimated to save US$7.3 million per year in dyke maintenance (Reid & Huq, 2005). In addition, almost 8,000 local families have been able to improve their livelihoods and thus their resilience by harvesting marine products in the replanted mangrove areas (Reid & Huq, 2005).
It has been argued that healthy natural ecosystems are more effective than man-made structures in coastal protection (Costanza, Mitsch, & Day, 2006). For example, the devastating effects of the 2005 ﬂood in New Orleans could partially have been avoided, if the wetlands surrounding the city had not been modified by humans, thus preventing the delta system absorbing changes in water ﬂows (Costanza et al., 2006). The problem is, due to anthropogenic stressors, not many coastal habitats are healthy or in a natural state. This is something that restoration aims to change, but to really make a difference, we have a long road ahead.
Significant mitigation of greenhouse gas emissions is the most crucial action that can be taken to reduce the effects of climate change, but we also need to adapt to the predicted changes by increasing ecosystem management methods sensitive to resilience (Tompkins & Adger, 2004). Traditionally, ecological restoration is based on the idea that we want to return something to its former condition. But ecosystems are not stable or static, never have been, and never will be (Willis & Birks, 2006). The increased risk of climate change induced coastal hazards possesses a major challenge to New Zealand economically, socially and environmentally. We have approximately 18,200 kilometres of shoreline, and one of the highest coast to land area ratios in the world. Most of New Zealand’s towns and cities, including our capital city Wellington, are located by the sea. In order to survive, we need to embrace ecosystem-based solutions and aim to restore for resilience.
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Paper by Scheffer, M. and Carpenter, S.R. (2003)
Synopsis by Hannes Öckerman
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