Securing access to food and water providing ecosystem services for SIDS
A case study on the island of Tarawa, Republic of Kiribati
Mara Daamen (10773835) Sven Iversen (10461051) Darryl Holsboer (11051957) Timo Leemans (10785612) Interdisciplinary Project Fenna Hoefsloot
Word count: 7715 words without in text citation/ 8339 with in text citation 22-12-2017
Abstract
Climate change has severe consequences for natural and social systems worldwide, and small island developing states (SIDS) are often indicated as one of the most vulnerable regions in the world with regard to climate change. Increase in extreme weather events, rising sea levels and temperatures pose substantial challenges for these island nations. In this report the major threats and possible responses to ensure access to food and water provisioning ecosystem services are researched for one such SIDS: Kiribati. To give a complete answer to this question, this research has the following sub-objectives: 1) to describe the relation between the isolation of the island and aspects related to food and water provisioning ecosystem services, 2) to describe the drivers behind changes in these provisioning ecosystem services and 3) to assess the resilience of Kiribati’s food and water provisioning ecosystem services. In addition, a concept model that links essential drivers and components is presented, and used to identify intervention possibilities aimed at enhancing access to food and water provisioning ecosystem services. With regard to food supplies, the marine and reef systems are identified as key food sources. Especially inshore or reef fishing activities are important for small-scale fisheries and subsistence of households. A large part of the fish population is dependent on coral the system and changes of this system could have a significant impact on the fish stocks. Agriculture is the other big source of food supply. Kiribati and also Tarawa have little areas of arable land. Due to the vulnerability and the isolation of reef islands water is a scarce resource. Similarly to food resources, water resources are affected by external drivers such as sea level rise, ENSO and pollution. Possible responses in regard to agricultural practices are implementing diverse agricultural systems, education about sustainable farming and promoting urban farming. With regard to coastal erosion future coastal structures should be strategically placed to prevent sedimentation and beach mining should be prohibited. Possible responses that specifically target water availability are numerous but expensive. Important however is: the improvement of efficiency, as 50% of all freshwater is lost from piping systems, the decrease of pollution preferably by means of a modern sewage system and strategic protection of the coast.
Table of Contents
1. Introduction 4
2. Theoretical framework 6
§2.1. Isolation in relation to SIDS and food & water 6
§2.2. Food and water providing ecosystem services in relation to SIDS and climate change 7 §2.3. Resilience in relation to food and water providing ecosystem services on SIDS 8
3. Selected method & data 10
§3.1. Method 10
§3.2. Data 11
4. Results 12
§4.1. Conceptual model of Kiribati’s food provisioning ecosystem services 13 §4.1.1. Isolation in relation to food providing ecosystems services 13 §4.1.2 Drivers behind alteration in food providing ecosystem services 14 §4.1.3. Resilience in relation to food providing ecosystem services 16 §4.2. Conceptual model of Kiribati’s water provisioning ecosystem services 18 §4.2.1. Isolation in relation to water providing ecosystems services 18 §4.2.2 Drivers behind alteration in water providing ecosystem services 19 §4.2.3. Resilience in relation to water providing ecosystems services 19
5. Conclusion and discussion 20
§5.1 Food 20
§5.2 Water 20
6. References 22
Appendix A 28
1. Introduction
Climate change has severe consequences for natural and social systems worldwide. Small island developing states (SIDS) are often indicated as one of the most vulnerable regions in the world with regard to climate change. The increase in extreme weather events, rising sea levels and temperatures poses substantial challenges for these island groups (UNFCCC, 2005). The Intergovernmental Panel on Climate Change (IPCC) predicts that the global mean sea level rise will be between 0.26 to 0.82 meters in 2081-2100 in comparison with 1986-2005, which will have devastating effects on low-lying islands in the Pacific ocean (IPCC, 2014). A rise in sea temperatures could cause massive coral bleaching and consequently the collapse of entire marine ecosystems, on which island communities predominantly depend (Brown, 1997; Hughes et al., 2017). Extreme weather events, such as tropical cyclones, extreme droughts, flooding el Nino and la Nina events, are predicted to become more severe and frequent in the nearby future and will cause destruction of ecosystems, homes and infrastructure (IPCC, 2014; Kuleshov et al., 2014). Thereby, the change in climate will have a severe impact on the terrestrial ecosystems and services (Mortreux & Barnett, 2009). According to Mortreux and Barnett (2009) climate change can cause saltwater intrusion, extinction of species, and a decrease in agricultural productivity.
Since 1990 multiple SIDS have united themselves in the Alliance of Small Island States (AOSIS). These SIDS have several aspects in common such as little habitable land, small populations, high population density, isolated, increasing pressure on island resources, extremely prone to extreme weather events, scarce in fresh water supplies, high degree of biodiversity and low economic power (UNFCCC, 2005). It is estimated that SIDS contributed less than 1% of the greenhouse gases, but probably will experience the most negative effects of climate change (UNFCCC, 2005 It is internationally recognized that multiple SIDS will become uninhabitable in the future due to climate change. Due to these features many SIDS have already trouble to meet food demands of all inhabitants due to their small natural resource base and increase in populations. In addition, climate change will put even more pressure on the island resources and it will therefore be even harder to meet the food and water demands of island communities in the future (FAO, 2004).
One of these island states, which is projected to be one of the fist nations that will become uninhabitable or even entirely submerged as a consequence of climate change, is the Republic of Kiribati (Algood & McNamara, 2016; The Republic of Kiribati, 2015). Kiribati covers an area of 3.5 million km2 in the Micronesian region, and consist of 33 atoll islands. The country is one of the poorest in the world, and earns 43% of its GDP with fishery, while also being heavily dependant upon international development aid (Kiribati, Republic of, 2015). More than half of the population of around 100,000 (CIA, 2017) lives on the island of Tarawa, the biggest island of the country, with the population being particularly concentrated on Tarawa’s southern part (see figure 1.1). As such, the main focus of this research will be on Tarawa.
Currently 5% of Kiribati’s entire population is food insecure (World Bank, n.d.). Kiribati has extensive reef and marine systems, that are key resources for providing food and employment (Campbell & Hanich, 2014). Furthermore, there is some agriculture practice on the islands but mostly for subsistence (Kiribati, 2015). For their water supply they mainly rely on precipitation and groundwater sources, the latter of which comprises roughly 85% of the total water availability (White & Falkland, 2011). It is expected that climate change will put significant pressure on the provisioning services of both water and food of Kiribati in the future (White & Falkland, 2011). It is therefore important, with regard to climate change, to examine if Kiribati in the future can still produce enough food and has enough water supplies to ensure both food and water demand for all inhabitants.
With the current trends, policymakers will face difficult decisions as ecosystems will degrade and ecosystem services tend to disappear and the vulnerability of island communities will increase. As a result of (local) climatic change, households are already undertaking several adaptation measures, including the building of physical defences, relocation, reducing expenses, working extra hours, and sell assets (Allgood & McNamara, 2016). At governmental level, various measures are undertaken as well, mostly aimed at coastal strengthening or restoration (e.g. planting mangroves, reducing coastal erosion) (Kiribati, 2015).
This research therefore focuses on the question: “What are the major threats and possible responses to ensure access to food and water provisioning ecosystem services on Tarawa, with regard to climate change in 2050?”. To give a complete answer on this question, this research has the following sub-objectives: 1) to describe the relation between the isolation of the island and aspects related to food and water provisioning ecosystem services, 2) to describe the drivers behind changes in these provisioning ecosystem services and 3) to assess the resilience of Kiribati’s food and water provisioning ecosystem services. In addition, a concept model that links essential drivers and components is presented, and used to identify intervention possibilities aimed at enhancing access to food and water provisioning ecosystem services. In this research, system thinking will be deployed to visualise the complex socio-ecological interactions between drivers. This will give insights on which interactions exist, and how optimal response policies can be designed (Villa et al. 2011).
The remainder of this report is organized as follows. First, a theoretical framework will discuss three interdisciplinary concepts related to SIDS, food and water demands. This will be followed by our Figure 1.1. Tarawa, the main island of the Republic of Kiribati (Google Maps, 2017)
selected method and data. In this chapter will be described how the chosen method helped to answer the main question. The results will be divided in a food and water section. In both sections three interdisciplinary concepts will be discussed respectively to food and water. In conclusion, the major threats for future food and water supplies and possible key responses will be summarized.
2. Theoretical framework
The following research sub-aims were presented in the introduction:
1) Describe the relationships between Kiribati’s isolation and aspects related to food and water providing ecosystem services;
2) Describe the drivers behind changes in these food and water providing services; and 3) Assess the resilience of these services.
Three concepts are central in these aims: isolation; food and water providing ecosystem services; and resilience. In this chapter, these concepts will be elaborated upon in relation to SIDS. Isolation in the first paragraph, food and water providing ecosystem services in the second, and finally the concept of resilience.
§2.1. Isolation in relation to SIDS and food & water
Islands are confined systems due to their physical distance to other landmasses, and consequently deal with various external and internal pressures (Paulay, 1994). Probably the most important consequence of such physical isolation on the internal part of an island system, is a high dependency on their local and often limited resource base, and a resulting vulnerability to resource failure (e.g. harvest failure) (Royle, 1989). Compensating for this resource scarcity by means of importing might be difficult as well, as island isolation is positively correlated with import costs, which is also true for food and water resources (Bass & Dalall-Clayton, 1995). In addition, small islands generally have a limited water catchment, and the resulting lack of freshwater supplies regularly hampers their economic development (Royle, 1989). Although research into these food and water resource-related phenomena has not received much attention since Royle’s (1989) article, his account of commonalities between island systems from a human geography perspective provides theoretical insights that are still useful today (as the basic mechanisms underlying these commonalities have not changed since).
A second set of internal pressures stems from the fact that island isolation is negatively correlated with species richness and positively correlated with the chance of extinction due to stochastic events (MacArthur & Wilson, 1976). As small islands often have relatively small populations of species, these tend to be more vulnerable with regard to changes in the system (Paulay, 1994; Kier et al., 2009). This has two consequences related to food providing ecosystem services. Firstly, small populations and low species richness (especially in plant species) results in little diversity in the gene pool. Less diverse populations have bigger changes to go extinct all at once, and are thus less resilient to disturbances. Agricultural production based on low species richness and low genetic diversity are thus vulnerable to change. A small change in the system may render it impossible for a particular kind of crop to grow on the island (Thaman, 2008). Secondly, one of the biggest threats for island species are invasive species. Due to globalization and an increase in global trade, past biogeographic barriers are breached and mass migration of species to remote and isolated areas, such as SIDS, is possible (Mooney & Cleland, 2001).
These non-native species end up in regions where their natural predators and competitors may not be present. In addition, on many island special niches are not occupied yet. Furthermore, continental species are generally more exposed to different kinds of pressures than island species. Therefore, it is possible for many non-native island species to proliferate quickly and become serious competitors of native species (Mooney & Cleland, 2001). Competition for resources with native species can have negative impacts, such as extinction of food crops or edible marine species.
Apart from internal pressures, SIDS are vulnerable to external pressures and natural disasters as well. In particular reef islands are widely perceived to be vulnerable to climate change and sea level rise (Briguglio, 1995; Woodroffe, 2008). Flooding, inundation, erosion and intrusion are recognized to be important processes that impact the coasts of SIDS (Woodroffe, 2008). Flooding and inundation are often used interchangeably, but are two different processes. The former occurs periodically and is triggered by for instance storms and precipitation, while the latter is a permanent submergence of areas due to for instance sea level rise (Flick et al., 2012). Erosion is the removal, dissolution and subsequent transportation of material, while intrusion is the salinization of freshwater due to diffusion of salt water (Christopherson, 2015; Woodroffe, 2008). These processes are strengthened by extreme weather events, such as storm surges, cyclones and droughts.
Two additional source of external pressure are economic. Firstly, isolation results in a disadvantage in international trade as transportation costs will always be higher compared to the mainland, making food imports more expensive and exports less profitable (Royle, 2001). Secondly, small islands often find themselves unable to profit from economies of scale, which may make basic economic activities, like water purification facilities, less efficient and more expensive (Royle, 1989).
Finally, isolation can be deployed as a resource as well: it’s beauty might attract large groups of tourists for example (ibid.).
§2.2. Food and water providing ecosystem services in relation to SIDS and climate change
Providing ecosystem services are defined as: “the material or energy outputs from ecosystems’’ (Biggs et al., 2017), and these include water and food outputs. Ecosystem services of SIDS are under pressure for various reasons. As terrestrial resources are often limited, marine and reef ecosystems are indicated as key food providers for SIDS. Indeed, Pacific SIDS have amongst the highest per capita fish consumption worldwide (Huelsenbeck, 2012). Food provisioning is recognized as the key service of reef ecosystems, providing some SIDS in the Pacific with both inshore subsistence fishing, as well as commercial offshore fishing (Huelsenbeck, 2012; FAO, 2004). However, coral reef systems provide SIDS with a broad range of additional services such as, coastal protection, recreation, biodiversity, and medical resources (Moberg & Folke, 1999). Additionally, fishery is a source of employment and income (Samaila, Dyck & Cheung, 2013).
Agriculture provides island communities with an additional food source. However, because of the limited land area, scarcity of fertile land, small domestic markets and the high cost of developing infrastructure on SIDS, most agricultural practices are often small-scaled (FAO, 2014; Singh, 2012). Furthermore, is there generally limited investment in commercial agriculture and most farming is used for subsistence. Therefore, is most agricultural products uncompetitive in comparison with import products (FAO, 2014). In addition, soil fertility ranges widely across islands. On volcanic islands soils are generally quite fertile with high water capacities and abundance of nutrients, while on reef islands soil fertility is poor, due to a high alkalinity, coarseness of soil material, lack of organic matter and shallow soil depth (Woodroffe & Morrison, 2001; Perret & Dorel, 1999). The soils on reef islands
mainly consist of lithosols and regosols of the texture class sandy loam and loamy sand, which suggests poor water retention but good permeability (Woodroffe & Morrison, 2001; Rawls et al., 1982).
As last, many SIDS have limited freshwater resources (UNFCC, 2005). On these islands even small increases in sea level rise are believed to have a significant effect on the thickness of the freshwater lenses, with an 0.1 m increase in sea level corresponding with a 60% reduction in thickness. A freshwater lens is defined as a pocket of groundwater, which floats directly above a layer of denser salt water. This source of freshwater is supplied and replenished by precipitation (Kundzewicz et al., 2008).
As was stated before, islands and its providing services are vulnerable to external processes. Sea level rise is one of three important drivers that will be discussed in this report and it affects all SIDS in one way or another. The future sea level rise will have big impacts on agricultural practices on these islands. As first, there will be more flooding, which will decrease the area of agricultural lands. Thereby could intrusion negatively affect the quality of these lands (Kelmen & West, 2009).
Additionally, for islands in the pacific the El Niño–Southern Oscillation (ENSO) is a crucial driver. It is defined as an extended period of sea surface temperature rise in the Eastern and central pacific and an increase in atmospheric pressure in the West of the Pacific. In addition, this period lasts for at least 6 months with an 0.5 celsius or greater mean temperature deviation of the sea surface (Trenberth, 1997). The ENSO can be divided in two phases El Niño and La Niña. The former is characterized by higher than average SSTs, while the latter is characterised by lower than average SSTs (ibid). The effects of ENSO are perceived around the globe, but are most apparent in and around the pacific, with droughts commonly occuring in the West pacific and floods occuring in the East pacific (Cane, 1983; Dilley & Heyman, 1995).
Lastly, anthropogenic activity in the form of pollution, which puts pressure on coral reef systems and water resources. Pollution can be defined as a type of contamination that negatively impacts among others the health, growth rate and comfort of organisms in an ecosystem (Clark et al., 1989).
§2.3. Resilience in relation to food and water providing ecosystem services on SIDS
Islands like all other systems have a form of resilience. The resilience of natural and social systems are two related, though somewhat different concepts (Adger, 2000). Resilience for natural systems is often defined as the ability of such systems to recover from disturbances or to return to a pre-disturbance state (Wilson, 2017). Holling (1973), for example, defined ecological resilience as follows: “the amount of disturbance that an ecosystem could withstand without changing self-organized processes and structures”.
A hypothesis related to resilience is the insurance hypothesis described by Yachi and Loreau (1999). They proposed that more biodiversity is a buffer against changes in the environment or system, because different species respond differently to changes. Therefore, if multiple species perform similar functions and one of these species fails in performing this function, other species will prevail, hence is the system more resilient and more productive in changing environments. (Yachi & Loreau, 1999). However, SIDS have a little specie richness and therefore, according to this hypothesis, would their systems be less resilient against changes. That these systems are less resilient has severe consequences for food and water resources in regard to climate change and human-related activities. For example, on many small islands communities historically managed their agricultural systems sustainable with a mix of diverse living organism, known as agrobiodiversity, therefore there are multiple species performing similar functions (Thaman, 2008). These systems were adapted to the island environment for generations.The mix of especially genetically diverse plants, makes the agricultural system more resilient, because different crops may react differently on certain changes in the systems, such as pests,
diseases and unusual weather patterns (Gonzalez, 2012). However, these traditional farming practices related to agrobiodiversity is disappearing, because of the increase in monoculture, urbanization, lifestyle change and monetization with as main driver high-varieties non native crops replacing traditional crops (Thaman, 2008; Gonzalez, 2011) The replacement of these traditional crops and wild varieties results in genetic erosion and thus the loss of resilience. Both Thaman & Gonzalez (2008; 2011) emphasizes that education and research has to be done to reintegrate local and historical crops and farming practices in combination with modern agricultural practices, such as plant breeding.
In contradiction many reef systems are very diverse and complex and would therefore, according to the insurance hypothesis, be very resilient. However, multiple researchers claim that a coral reef systems can switch to an alternate state: from a coral-dominated to fleshy seaweed. This shift is mainly caused by coral bleaching: the process whereby stressed and overheated corals expel a microalgal symbiont and turn pale and eventually die (Hughes et al., 2003). It is thus important to understand when certain ‘tipping points’ are reached and a system will shift into an alternate state. A tipping point is reached, when a small perturbation suddenly has a disproportionate reactions, such as shifting to another steady state (Scheffer et al., 2001).An alternate state means that certain key processes of a system change and that systems as a whole will perform alternative behaviour (Holling, 1973). Scheffer et al. (2001) emphasize that once a system is shifted to an alternate state, it may not easily return to the original steady state. The switch of reef systems for alternate states could have devastating effects for local communities depending on it for food. In the case of reef systems multiple stresses, both geo-physical and human-related, are identified which decrease the resilience of reef systems such as 1) increase of sea water temperature, 2) higher oceanic CO2 levels, 3) pollution, and 4) overfishing (Adger, 2006; Kayenne et al., 2014). Some local stresses can be mitigated, which will enhance the resilience. However, some stresses are caused on a global level, such as the increase of greenhouse gases and warming of sea temperatures, and to these stresses interventions on local level are not possible.
However, multiple hypotheses are proposed to prevent a coral systems from shifting to alternate algae dominated state. For example, Hoolbrook et al., (2016) proposed that the increase of herbivorous fish could prevent the proliferation of algae due to grazing and therefore may the decrease of fishing for hebirvouric fish prevent the shift to alternate states. Thereby, is there some evidence that some coral species can evolve to become more heat tolerant and natural selection may result in coral species that are better adapted to the changes in sea water temperature and even the increase of CO2 levels . Also preventing the runoff of excess of nutrients could improve the resilience of reefs (Hughes et al., 2007). Resilience is also perceivable in coastal systems and is similarly related with the aforementioned vulnerability. In coasts three states can be described, an accreted state, an eroded state and an intermediate state. In the accreted state beaches are steep, which naturally reflects wave energy (Woodroffe, 2007). Sedimentation can be defined as the deposition of fine material such as sand, clay and silt by water, ice and wind (Christopherson, 2015). In the eroded state beaches are flat and sandbars are formed. The intermediate state is self-explanatory and is a combination of the aforementioned states (Woodroffe, 2007).
Sedimentation and erosion processes behave differently depending on the type of balance that is maintained, otherwise known as an equilibrium. There are three types of equilibrium namely: static, metastable and dynamic. In a static equilibrium beaches do not react to change and stay in their current state. Whereas in a metastable equilibrium beaches shift between an eroded and accreted state. Most beaches are however in a form of dynamic equilibrium, which is a complex balance of sedimentation and erosion, where the island is gradually evolving (ibid).
According to research spanning 60 years conducted by Webb & Kench (2010) most researched reef islands in the pacific have persisted even with rising sea levels. Of the 27 studied islands 86% were discovered to be stable or to be increased in size, while 14% were perceived to be decreased in size.
This in itself does not imply that islands are unaffected by rising sea levels, but it does suggest that islands are dynamic and can compensate for rising sea levels.
Moreover, anthropogenic activity also contributed to the growth of certain islands by means of land reclamations (ibid). Though it is unclear what this implies for the resilience of islands in the future, as anthropogenic influences have been linked with negative alteration to coastal processes (Woodroffe, 2007).
3. Selected method & data
§3.1. MethodThe way the Republic of Kiribati will cope with climate change can be seen as a complex problem, because there is a large amount of actors and interactions involved (Pimm, 1984; de Groot, 2002). In the case of Tarawa the natural and social systems are extremely intertwined, because of the high dependency of the community on the local ecosystem services and the social and physical isolation as has been mentioned in the theoretic framework. Therefore, is it impossible to understand how the systems work without an interdisciplinary approach. Because explicit uncertainty is crucial in decision-making, it is important to clarify the interactions inside an environmental and socio-economic system such that easier and more efficient adaptation or mitigation policies can be found (de Groot, 2002).
In this report there will be made use of system thinking to visualise the complex socio-ecological interactions between drivers. Systems have the capacity to clarify correlations and connections between drivers inside a interdisciplinary system, thereby eliminating knowledge gaps and uncertainties. In this research a comprehensive stock and flow model will be developed which can contribute to optimal decision making (Fisher et al, 2007). This model will contain all involved biological, human geographical and physical components and their reciprocal interactions in which stocks are a quantities of material and flows are actions which affects the quantities of the stocks (Meadows, 2008).
The methodology used in this research is based on a conceptual framework used to show links between ecosystem services, human well-being and change processes (Daily et al. 2009). The Ecosystems and Services, consisting of the most important processes and concepts that play a role inside the ecosystem
Figure 3.1. A methodology, used by (Daily et al. 2009), to improve decision making for important ecosystem services. This research will follow the same approach. However, instead of quantizing the provision services (as is focussed on in ‘Values’), there will be made use of semi-quantitative data in order to visualise the key relations with the provisioning services. The visualisation will be explained further on.
which is to be investigated, are already discussed inside the theoretical framework. In order to evaluate the two provisioning services (water and food) and the direct and indirect processes on which the provisioning services depend, there will be made use of secondary data. No primary data will be used due to the problems of long-distance, expenses and the availability of time. A vast amount of trustworthy data has already been produced about climate change and there has been done scientific research on the Republic of Kiribati (Appendix B). However, due to lack of quantitative data, this research will make use of semi-quantitative data consisting of either increases or decreases quantity of services with respect to the (in)direct correlations between natural and social processes. Therefore, this research is primarily focussing on a better understanding of the interrelations inside a socio-ecological system and on integrating research into the development of new solutions to complex problems, rather than evaluating them.
These relations will be presented inside a diagram, which will give a plain overview of the most important relations at hand, thereby providing knowledge on what socio-environmental processes are expected to influence the resilience of the two provisioning services (see step 2 in figure 3.2). Together with these relations, a comprehensive stock-flow model will be generated that will give a complete overview of the food and water system in Kiribati. To do so, there will be made use of integrating techniques, such as redefining concepts that are contained in multiple disciplines and organising them by finding relationships between them. As this research focuses on two provisioning services, two concept models (one for every services) will be provided that will show the (in)direct processes that are relevant to these services.
With both a comprehensive concept model and a diagram which explains the direct relations between variables that are present inside the model, there can be found key relationships that have a considerable influence on either one of the provisioning services that are being investigated. Once these key relationships are found, there can be further explored what possible responses or coping mechanisms there are to increase the security and resilience of both provisioning services. This will also reveal the importance that ecosystem services must be explicitly and systematically integrated into decision making by individuals, corporations and governments.
However there are some limitations to this methodology. As this is a semi-quantitative approach (due to lack of quantitative data), there is no real certainty to the magnitude of the key relationships between variables inside the system, since most relations are only known to be either positive or negative. Still this methodology can provide strong suggestions to improve relationships inside the socio-ecological system of Tarawa that can contribute to the security and resilience of both provisioning services.
§3.2. Data
To follow the methodology, a diagram will be presented with the direct relations between the natural and social processes to generate an overview of the most important relations in the socio-ecological system of Tarawa. The relations are formulated with respect to the prospected trend of temperature, sea level rise, CO2-increase and precipitation in percentages which are provided in table 3.1 below and
are based on the latest IPPC report. These values are based the average scenario which has a relative high likelihood of occuring in the future (CDKN & ODI, 2014, Stocker et al, 2014). With this approach, the uncertainty of future events is still present since only one single possible prediction is evaluated. However, as these predictions provide a good estimation of future events, it will be sufficient to evaluate on one scenario. Besides, there is not enough data available to focus on more scenarios and it would reduce the possibility of finding optimal responses to future events.
Inside the diagram (which will be presented in Appendix), quantitative data is provided when there was knowledge on the relation with respect to the prospected trend, otherwise (when quantitative data was lacking) there is only provided whether there is a ‘positive’ or ‘negative’ relation. The aim of this diagram is to substantiate the concept models presented in the results and to find, in combination with the concept models, possible responses and coping mechanisms in the future. With the scope of 2065, this research limits itself to a relative short term. However, as the island communities are currently being exposed by effects of climate change and this will only increase in time, it is of higher importance to focus on the short term responses then long term, to prevent rapid and unexpected collapse of the island system.
Prospected trend
Temperature (℃) (CDKN & ODI, 2014) 1.3
Sea level rise (mm) (Stocker et al., 2014) 18-33
CO2 concentratie (ppm) (Meinshausen, 2011) 483
Increase precipitation(%) (Australian Bureau of Meteorology and CSIRO, 2011; Legates & Willmott, 1990; Stocker et al., 2014)
2.5-7.4%
Table 3.1. Trends based on the IPCC 5th risk assessment (2014). These are predictions for 2065.
4. Results
For both the food and water provisioning ecosystem services, conceptual model were developed. These models show how different biological, geophysical, and social components interact, and how humans (can) get access to these ecosystem services. Here, both conceptual models are presented, and their major components discussed.
§4.1. Conceptual model of Kiribati’s food provisioning ecosystem services
§4.1.1. Isolation in relation to food providing ecosystems services
Due to the isolation of the island of Tarawa, its population is heavily dependent on a scarce natural resource base (Borovnik, 2005). In figure 4.1.1.a, a portion of the system is presented, showing the relations between key variables and the isolation and vulnerability of Tarawa. As a result of its small resource base, Tarawa is extremely dependent on its reef and marine ecosystems, with 30% of export consisting of fish, and fishing licenses paid by foreign fishing boats accounting for almost 43% of the GDP. In additon, almost 80% of the households on Tarawa are engaged in in-shore or coral reef fishing activities for subsistence. The largest part of their daily needed protein intake is provided by these activities (Bell et al., 2009; Campbell & Hanich, 2014).
A further effect of Tarawa’s isolation and small resource base is a high dependency on overseas employment (mostly on foreign merchant ships or tuna vessels) as the opportunities for economic development on Tarawa itself are limited (Borovnik, 2005). As such, Tarawa’s population depends upon remittances for their daily incomes (e.g. for buying fish or other food products). Remittances send back by seafarers accounted for almost 10% of Kiribati’s GDP in 2015 (World Bank, n.d.).
Figure 4.1 Conceptual model for food provisioning ecosystem services. The arrows between different concepts show the relationship with (-) being a negative relationship and (+) being a positive relationship. The model is splitted in four different regions from top till bottom: the interaction of natural components, interactions of social components and the inflow and outflow of the food supply.
As mentioned, many small islands have low species richness, which makes them vulnerable to invasive species (Mooney & Cleland, 2001). Tarawa deals with invasive species as well. Currently, 43 flora and fauna species have been identified as invasive, being a potential threat for the island’s ecosystems. This situation can become more severe, as 74 additional species have been identified that could become invasive in the future (Space & Imada, 2004). One example of an invasive species that was introduced, is Tilapia, a freshwater fish that threatens the milk fish, which is traditionally consumed around Tarawa (ibid.). The indirect effect of invasive species on the food resources of Kiribati is very uncertain, however it will probably be negative in the future, although sometimes non-native species can become new food resources (Pechjar & Mooney, 2009).
Subsequently, this isolation makes Tarawa vulnerable to processes that impact the coast, as is illustrated in the relation figure 4.1.1.a. Inundation is projected to increase according to the predicted trend ranging from 40 to 67% of land inundated by 2050, of which
north Tarawa is expected to be affected the most and which can be attributed to the rise in sea level (Storey & Hunter, 2010). This will negatively impact the already small agricultural areas, such as in taro pits where salinisation will take place, leading to crop failure (mainly due to a decrease in soil fertility) and contaminated water (Woodroffe, 2008; Terry et al., 2013).
Similarly flooding is expected to rise due to increased cyclone activity in the pacific. Kiribati and Tarawa are outside the region where cyclones form, but are nevertheless impacted by storm surges that result from cyclones. Effects of flooding due to storm surges are similar to inundation and are especially troublesome for water resources, which are discussed in section 4.2.1 (Terry et al., 2013).
§4.1.2 Drivers behind alteration in food providing ecosystem services Fish
On South-Tarawa urbanization is pressurizing reef systems along the coast, because small-scale fisheries may overexploit inshore fish stock to provide enough fresh fish for local markets. This may have devastating effects for the coral systems, because less grazing could lead to an increase in algae and finally a shift to an algae dominated systems (Hoolbrook et al., 2014). This phenomenon is also observed in the lagoon of Tarawa by Beets (2001). In his research he proved that at the more accessible locations in the lagoon more fishing takes place and that there coral patches had higher percentages of algae in comparison to less accessible places. He also showed annually decline of the fish stock in the lagoon due to overfishing and more efficient fishing tools (Figure 4.1.2.b). Paulay & Kerr (2001) showed that coral covers at the southern part of the lagoon had less coral cover, were less diverse and also had higher percentages of algae cover than northern patches in the lagoon. They argue that the southern part is more nutrient-rich, because of pollution and runoff of sewage water in the lagoon, which leads to proliferation of algae. However, the coral systems around Tarawa has an extremely high yield per km2 with 23 tonnes/km2/year in comparison to the average yield of 3 tonnes/km2/year (Dalzell, Adams & Polunin, 1997; Bells et al., 2013). Nonetheless, it is expected there will be a large decline in coral cover due to warming of sea water (see table 4.1.2.c.). Unfortunately data is lacking about the are of coral cover around Tarawa. Thereby, there is no recent research available to the current status of the Figure 4.1.1.a. The relation of isolation towards principal variables inside the concept model
coral. Nevertheless will reef fish stocks, which are most important for small-scale fisheries and subsistence fishing, decline in the future, because of the decrease of coral cover (Figure 4.1.2.b).
In addition to coral fishing, there is also oceanic fishing. Kiribati has an enormous EEZ which is amongst the regions with the biggest tuna populations worldwide. The amount of tuna is affected by ENSO events with higher catchments in El Niño years, when temperatures are higher than average (Campbell & Hanich, 2014). Under normal conditions tunas are primarily found in the western pacific where temperatures are greatest also known as the warm pool, however during an El Niño event tuna
migrate east towards Kiribati, as the pool of warm water migrates east (Lehodey et al., 1997). Bell et al., (2013) even predicts 5% higher catchments of tuna in the future. However, most of the large-scale and commercial fishing is done by foreign fishing companies and is therefore not a big source of food for the inhabitants of Kiribati. Also are these catchments almost never meant for local markets or consumption. However, oceanic subsistence and artisanal fishing contribute significant fresh tuna for local markets and could in the future provide food in compensation of the loss of reef fishing (Campbell & Hanich, 2014).
Agriculture
Another source for food is agriculture with coconut, banana, pumpkin, cabbage and pandanus identified as main crops produced on Tarawa. However, there is no official data about the amount of agriculture food produced on Tarawa (FAO, 2011). Tarawa has little space for agriculture and while in Kiribati as a whole 43% of land use is agricultural, only 2.5% of that is arable land (CIA, 2017). In addition, soils are quite infertile due to high alkalinity, which increases decomposition of organic material (Tonon et al., 2010; Woodroffe & Morrison, 2001). Moreover, due to sandy material leading to a lack of water retention and uniformity of soil due to removal of vegetation. This can be concluded from research performed by Woodroffe & Morrison (2001) on Makin island. Soil fertility on this island is representative for Tarawa, as most reef islands have similar soils and Makin is located in proximity of Tarawa (ibid) (Figure 4.1.2.b.)
Table 4.1.2.c Predicted decline of live coral due to seawater warming. These predictions are based on global data, therefore is it uncertain how locally corals will react (Bell et al., 2013; Frieler et al., 2013)
Figure 4.1.2.b Portion of the concept model, focussing on fish stock and its direct and indirect relations
Tarawa has a long history with agroforestry, however there is a trend of removing trees in agricultural systems due to the implementation of monocultures of cash crops, such as copra (Thomas, 2002). The removal of trees causes less diverse systems, which are more vulnerable to diseases, pests and changing weather patterns (Thaman, 2008). Thereby, due to the removal of trees erosion and thus soil degradation could increase. This will lead to less productive agricultural practices and a decline in yield (Figure 4.1.2.b). In additon, soil degradation also takes place when coasts are eroded, which on Tarawa is mostly attributed to reclamations and mining of beaches (Barnett & Adger, 2003; Biribo & Woodroffe, 2013). This can disrupt the natural balance of erosion and sedimentation, which is further elaborated upon in section 4.1.3.
As was mentioned before ENSO affects fishing stocks due to higher temperatures. It can however also lead to more extreme weather in the form of droughts and floods. In the case of Tarawa however droughts are predicted to decrease in intensity and frequency over the course of this century. Furthermore, while no concrete precipitation data is available, it can be stated that precipitation will increase for Tarawa according to the current trends. It can therefore be inferred that climate conditions for agriculture will improve with increasing temperatures, when omitting effects of sea level rise (Australian Bureau of Meteorology and CSIRO, 2011; Storey & Hunter, 2010).
§4.1.3. Resilience in relation to food providing ecosystem services
To enhance the resilience of (the population’s access to) food provisioning services both the marine, reef and agricultural systems have to become resilient against disturbances stemming from climate change and human-related activities. Multiple interventions to enhance the resilience of different parts of these system were already proposed by researchers.
With regard to reef fishing Bell et al., (2009) argues that new policy has to be implemented such as monitoring of fish populations, education to small-scale fishers about sustainable fishing, banning of certain non-sustainable fishing gears and diversification of the fishing resources to prevent overexploitation. As already observed is there at some locations in the lagoon of Tarawa a decline in fish stocks. Indicators have to be identified to keep fishing in sustainable boundaries. Therefore, research have to be conducted to key indicator species. Thereby should pollution and the runoff of sewage in the lagoon be halted. Initiatives to decrease the pollution of ocean and lagoon waters is to implement governmental runned sewage systems and education for locals about the impact of waste. Thereby should organic waste be recycled to create compost and preventing excess amounts of nutrients runoff in the ocean and lagoon (Miller et al., 2004).
Figure 4.1.2.b Portion of the concept model, focussing on the relations concerning agriculture. The main interactions are flooding and inundation due to their negative influence on the water availability and fertility of the ground.
It is expected that till the year of 2030 inhabitants can still catch enough fish to maintain their protein intake of fish (Bell et al., 2013). However, redistribution to supply the urban area of Tarawa can become a big challenge, because of the distances, high costs of transport and poor infrastructure (Campbell & Hanich, 2014). Remittances could provide an alternative source of income to buy fish in stead of catching it, although this is complicated due to the so-called bubuti system (Borovnik, 2005). This local welfare arrangement system is deeply ingrained in Kiribati’s culture, and provides a set of informal rules according to which remittances are distributed among the extended familiy and community of a seafarer (ibid.). In short, those seafarers with a surplus are expected to share their remittances with members of their family and community, which enhances the resilience of those members against food insecurity. However, access to surplus remittances under the bubuti system is not equal to all, with parents of unmarried sons and dwellers of cities are better off than parents of unmarried daughters and outer island dwellers (ibid.).
With regard to agriculture, several interventions to enhance the resilience of the agricultural system are possible. First of all both Thomas (2002) as Thaman (2008) emphasize the importance of diversification and agroforestry in the agricultural system to make the system more resilient against pests, diseases and a changing environment. Therefore is it important that traditional knowledge in regard to modern and traditional farming techniques and crops can provide sustainable and resilient systems. Research has to be conducted to which mixture modern and traditional agricultural techniques and crops would create sustainable and resilient systems . Also small-scale farmers should be educated about sustainable farming practices, such as sustainable ways to handle waste (Miller., 2004). The FAO argues that on other less inhabited island could be space for agriculture, however shipping is quite unreliable in Kiribati, which causes fluctuating food prices (FAO, 2011). Another proposed by intervention Thomas (2002) to make the population less food insecure is urban gardening. He states that education is needed to learn people about urban gardening, which could also create job opportunities for unemployed.
Due to Tarawa consisting entirely out of coast, a resilient coast equates a resilient island. In the previous sections erosion was stated as an important process that affects vulnerable islands. On Tarawa maximum erosion rates of 0.2 mm/year have been perceived in the Northern part of the island and maximum erosion rates of 1.2 to 1.8 mm/year have been perceived in the Southern part of the island. This can be attributed to the greater anthropogenic influence in the south, where most of the people live and many reclamations have occurred. The land area of Tarawa increased by 20% from 1968 to 1998, of which 81% was due to major reclamations (Biribo & Woodroffe, 2013).
In comparison sedimentation rates in North Tarawa were discovered to be 0.5 mm/year, while sedimentation rates in South Tarawa were 1.3 to 1.4 mm/year. As a whole this implies that coasts are accreting in the north, but eroding ever so slightly in the south. Coastal structures are believed to be the cause, which disrupt the natural transport of sedimentation (ibid).
Further reclamations are therefore deemed unsustainable, as are other activities such as beach mining. More education on the subject of sustainability of the island is required, as is the prohibition of beach mining. In addition, future coastal structures should be strategically placed to prevent disruption of sedimentation (ibid).
§4.2. Conceptual model of Kiribati’s water provisioning ecosystem services
§4.2.1. Isolation in relation to water providing ecosystems services
The isolation of islands also influence its water availability. On tarawa roughly 80% of all water is retrieved from groundwater, which in itself is dependent on the size of the island (White, 2011). Similarly to food resources, water resources are vulnerable to processes that impact the coast. In addition to flooding, inundation and erosion however intrusion is an important process. Storm surges are believed to increase intrusion in islands that are otherwise unaffected by it such as Tarawa due to overwash of saltwater(Terry et al., 2013). Intrusion is therefore expected to increase, however no scientific evidence is available to suggest that on Tarawa intrusion is worsened by sea level rise, as recharge of freshwater is dependent on ENSO (Storey & Hunter, 2010; Woodroffe, 2008; White & Falkland, 2010).
Erosion is a process that is not usually mentioned when examining water availability, but it can also introduce additional intrusion, due to loss of land at the edges of aquifers. This is normally only applicable for islands directly impacted by cyclones (Terry et al., 2013), however as was mentioned in section 4.1.3, beach mining also leads to erosion, which means the same applies for Tarawa.
Figure 4.2 Conceptual model for water provisioning ecosystem services. The arrows between different concepts show the relationship with (-) being a negative relationship and (+) being a positive relationship. The model is splitted in four different regions from top till bottom: The interaction of natural components, interactions of social components and the inflow and outflow of the water supply.
Furthermore, while unrelated to intrusion droughts also contribute to the decrease of freshwater availability (Storey & Hunter, 2010).
§4.2.2 Drivers behind alteration in water providing ecosystem services
The drivers of water and food resources are similar, though slightly different in interaction. On tarawa ENSO is crucial in understanding the water availability, for the weather plays an important role in the replenishment of the freshwater lens of the island. According to Storey & Hunter (2010), freshwater lenses on Tarawa can reach a maximum thickness of 30m under normal conditions and 6m during droughts. Droughts commonly occur during La niña events, while increased precipitation occurs during El niño events. Precipitation rates are however quite unpredictable on Tarawa, as models often fail to capture the variability of ENSO, which makes it impossible to create accurate precipitation predictions for climate changes (CDKN & ODI, 2014).
Nevertheless, El niño events have become more dominant over the last decades, which implies an increased water availability on Tarawa. This is may have been caused by climate change, which might indicate a further increase of El niño events in the future (Connell, 2015).
Sea level rise is another driver, of which the effects were mentioned in section 4.1.1 and 4.2.1. Flooding and inundation in particular are projected to increase, which decreases access of freshwater sources on the island (Storey & Hunter, 2010).
In addition pollution from sewage waste poses a threat to the water availability, due to the lack of modern sewage systems. Waste can enter freshwater lenses directly via taro pits or leach through the sandy soils, which are highly permeable (ibid; White & Falkland, 2010).
§4.2.3. Resilience in relation to water providing ecosystems services
With regard to resilience much has already been mentioned for food resources, which are also applicable here. Coastal protection is crucial in preventing erosion from taking place, which could decrease water availability and valuable agricultural land. One possible response to decreasing water availability is to increase efficiency. Water losses from piping systems can go up to 50% and is one of the most important issues in regards to water availability (White, 2011).
Related to piping systems is the improvement of the sewage systems on the island. Most sewage is not treated in a treatment plant. For this reason the construction of a reverse osmosis water treatment plant, while costly might be the best solution to increase water availability and decrease the pollution, as these plants can also be used to desalinate water (ibid).
Salinisation of freshwater is another problem on Tarawa, which frequently occurs during droughts and storm surges (Storey & Hunter, 2010). To conserve water introduction of drought and or salt tolerant crops could prove beneficial (Klein & Persson, 2008), while pumps could be used to remove salinated water from taro pits after a flood. The latter is very risky however and is best used as a last resort, as saline intrusion by storm surges only affects water resources in the short term (Storey & Hunter, 2010).
It can be concluded that many factors influence the water availability and it can be seen as the greatest obstacle for the island, as currently water availability is projected to be insufficient by 2030 (White, 2011). The complete diagram with all individual variables and their interrelations are presented in Appendix A. This diagram, as has already been mentioned in section 3, is used as substantiating material to the concept models and used to find possible responses to secure the acces to the two provisioning services on the island of Tarawa.
5. Conclusion and discussion
In this research two conceptual models for both provisioning ecosystems of food and water on Tarawa, Kiribati in regard to future climate change were developed. In this model all biological, socially and geophysical concepts and their interactions are described. With respect to these models, biggest threats and possible responses to these threats could be identified.
§5.1 Food
With regard to food supplies, the marine and reef systems are identified as key food sources. Especially inshore or reef fishing activities are important for small-scale fisheries and subsistence of households (Campbell & Hanich, 2014). A large part of the fish population is dependent on coral the system and changes of this system could have a significant impact on the fish stocks. On a global level, two major threats for coral systems are the increase in both sea temperatures and oceanic CO2, which will cause coral degradation (Adger, 2006; Kayenne et al., 2001). Unfortunately, on local levels, there are no possible responses to these threats. On local level overfishing and pollution can be identified as key threats (Beets, 2001; Hoolbrook et al., 2014). With regard to overfishing, research has to be conducted to key indicator species and elements, which could lead to temporarily a ban of fishing on certain species till populations levels are stabilized. Further responses could be education about sustainable fishing and ban of non-sustainable fishing gear (Bell et al., 2009). Also, runoff of nutrients in oceanic and lagoons water should be halted. This could be done by recycling of organic waste, implementation of a governmental sewage plan and education for local households about the implications of waste (Miller et al., 2004). Another response with big potential is the increase of offshore tuna fishing for local markets because tuna population is expected to increase in the future. However, redistribution and storage will become big challenges (Campbell & Hanich, 2014).
Agriculture is the other big source of food supply. Kiribati and also Tarawa has little areas of arable land (CIA, 2017). In addition are these soils quite infertile, because of the high alkalinity (Tonon et al., 2010; Woodroffe & Morrison, 2001). Tarawa has a long history with agroforestry, however, there is a trend in the removal of trees. This has two major implications: 1) An increase of erosion, which leads to soil degradation and 2) less diverse agricultural systems, which makes it more vulnerable to diseases and changing environments (Thaman, 2008). Another cause of soil degradation is coastal erosion and flooding due to sea level rise, reclamation and beach mining (Barnett & Adger, 2003; Biribo & Woodroffe, 2013). However, it is expected precipitation will increase, which possibly will improve environmental conditions for agriculture (Australian Bureau of Meteorology and CSIRO, 2011; Storey & Hunter, 2010). Possible responses in regard to agricultural practices are implementing diverse agricultural systems, education about sustainable farming and promoting urban farming. With regard to coastal erosion future coastal structures should be strategically placed to prevent sedimentation and beach mining should be prohibited (ibid.)
§5.2 Water
Due to the vulnerability and the isolation of reef islands water is a scarce resource. Similarly to food resources, water resources are affected by external drivers such as sea level rise, ENSO and pollution. Inundation, flooding, intrusion and erosion are all expected to increase in one way or another. No quantitative data for intrusion is available however with suggests that more research should be
performed on the influence of sea level rise in regards with intrusion on Tarawa. This lack of data extends to ENSO and its effect on Kiribati and Tarawa. Droughts are predicted to decrease and precipitation rates are predicted to increase, however no concrete quantitative data is available for the region of Kiribati. The accuracy of climate models are low and the variability is high. This data is however very valuable, as around 80% of all water on Tarawa is retrieved from the freshwater lenses in the ground, which is replenished by precipitation. Additionally, pollution further stresses the water availability, which is mainly caused by a lack of a modern sewage system.
Possible responses that specifically target water availability are numerous but expensive. Such as the introduction of salt and drought tolerant crops and construction of reverse osmosis water treatment plants. Important however is: the improvement of efficiency, as 50% of all freshwater is lost from piping systems, the decrease of pollution preferably by means of a modern sewage system and strategic protection of the coast.
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