Chapter 4 the Catchment to Coast Continuum

Chapter 4 The Catchment to Coast Continuum Wim Salomons, Hartwig H. Kremer and R. Kerry Turner Contributors: Elena N. Andreeva, Russell S. Arthurton, Horst Behrendt, Peter Burbridge, Chen-Tung Arthur Chen, Christopher J. Crossland, Jürgen Gandrass, Vjacheslav V. Gordeev, Nick Harvey, G. H. Hong, Bjorn Kjerfve, L. D. de Lacerda, Janet I. Marshall Crossland, Nicole Morcom, Eric Odada, Jozef Pacyna, Nancy N. Rabalais, Dennis Swaney, William J. Wiebe tions on fluxes and their subsequent impact on the coastal 4.1 Introduction zone were considered. In some cases, attention was paid to climate change. However, the challenge of identifying The policy and management challenge for coastal zones differences in culture and values was not met, (time- is to ensure the sustainable availability of coastal re- frames of hundreds of years) nor their effect on public sources under intense pressure from environmental policy and perceptions of coastal zone impacts. change. However, much of the environmental change Within LOICZ, a standardised framework of analysis pressures originate not from within the coastal zone but was developed to assess the impact of land-based sources, from the catchments, or river basins, that feed freshwa- in particular catchment basins, on coastal systems (see ter and materials into the coastal zone. Riverine inputs, Chap. 1 and Text Box 4.1). About 100 catchment–coastal along with oceanic forces, influence the geomorphology sea systems have been analysed through workshops and and availability of natural resources of the coastal zone. desk studies. In addition, individual assessments were The linkages between catchment–coastal processes and scaled up to continental regions. The activities of LOICZ- systems, the influence of climatic change and the impacts Basins have also resulted in more detailed studies of on and feedback effects from socio-economic activity are catchments in Africa (AfriCat) and in Europe (EuroCat) still poorly understood. (Fig. 4.2). One approach to better understanding of the catch- In the LOICZ-Basins assessments, the coastal sea and ment–coast linkage is to use retrospective information its associated catchment(s) are treated as one system and from the system in order to make predictions about its evaluated by consideration of the elements of the Driver– future behaviour. This requires an in-depth analysis of Pressure–State–Impact–Response (DPSIR) framework changes in processes and impacts that are the result of (Text Box 4.1; Fig. 4.3). The coastal response to land-based change in the biophysical system or its inherent variabil- activities is determined against socio-economic activi- ity and of those due to human impacts on the biophysi- ties so that results from natural and socio-economic sci- cal system (e.g., coastal engineering, conversion of ences have to be combined (Turner et al. 1998, Salomons wetlands, fishing) that have led to a significant loss of et al. 1999). For instance, impacts of socio-economic ac- coastal ecosystems and resources. Less well-known are tivities are modified by the biophysical settings of the the indirect changes originating from the catchment ba- catchment-coast-sea system. A similar level of socio-eco- sin that cause changes in flow of freshwater, sediments (Syvitski 2003, Syvitski et al. 2005), nutrients (Smith et al. 2003) and contaminants. The impacts of indirect changes are influenced by the source of the change, the time-scale over which it operates and the interaction of natural and socio-economic variables on the system (Fig. 4.1). 4.1.1 The LOICZ-Basins Approach During the LOICZ-Basins study, not all the components of Fig. 4.1 could be considered within the available resources and time-frame. Attention was given to assessments across a time-frame of 20 to 30 years. The impact Fig. 4.1. LOICZ-Basins. Natural and socio-economic inter-linkage of differences in biophysical and socio-economic condi- in the catchment–coast continuum 146 CHAPTER 4 · The Catchment to Coast Continuum Fig. 4.2. LOICZ-Basins Catchments and coastal regions evaluated (* resulting research projects) Fig. 4.3. LOICZ-Basins. a The catchment-coast continuum as one system; b the DPSIR framework nomic activity in a small mountainous river system will ments are a priority for the global LOICZ-Basins assess- have a different impact on the receiving coastal zone than ment. They dominate the global coastal zone (in Africa, a large lowland river system. for example, they characterise extensive parts of mon- Large catchments would at first seem to be obvious soon-driven runoff to the Indian Ocean). examples to be addressed within a global LOICZ synthe- The LOICZ-Basins assessment follows a hierarchy of sising effort (e.g., Amazon, Nile, Yangtze, Orinoco). How- scales which generate a composite regional picture. The ever, from the perspective of coastal change, the major scales range from: influence from land-based flows is more often generated by small to medium catchments with high levels of socio- local catchments, to economic activity. In small to medium catchments, national or sub-regional or provincial levels, to changes in land cover and use need much shorter time- full regional i.e., sub-continental or even continental. frames to translate into coastal change, and for any given magnitude of change usually exhibit more visible impacts The steps taken in an assessment are: than changes within large catchments where the “buffer capacity” against land-based change is higher, simply as 1. production of a list of coastal change issues and re- a function of basin size. Thus, small and medium catch- lated drivers in the catchment. 4.1 · Introduction 147 Text Box 4.1. The Driver-Pressure-State-Impact-Response Framework Wim Salomons, Hartwig H. Kremer, R. Kerry Turner The Driver-Pressure-State-Impact-Response (DPSIR) scheme port (including contaminants where appropriate) observed (Turner et al. 1998, Turner and Bower 1999) provides a standard- in the coastal zone as key indicators for trans-boundary pres- ised framework for site assessment and evaluation and adopts a sures within the water pathway. Indicators are designed to systems approach. The elements of the framework are: give an overview of the environmental status and its development over time and ultimately enable derivation of assimi- Drivers: resulting from societal demands, these are the activi- lative capacity limits, geomorphologic settings, erosion, se- ties with consequences for the coastal zone and include: urbani- questration of sediments, siltation and sedimentation, eco- sation, aquaculture, fisheries, oil production and pro-cessing, nomic fluxes relating to changes in resource stocks and flows mining, agriculture and forestry, industrial development, ports and changes in economic activity in monetary and other and harbour development and other land-use changes. terms. Pressures: processes affecting key ecosystem and social sys- Impact: effects on system characteristics and provision of tem functioning (i.e., natural and anthropogenic forcing af- goods and services, for example: habitat alteration, changes in fecting and changing the state of the coastal environment), biodiversity, social and economic functions, resource and serv- including: damming and other constructions, river diversion, ices availability, use and sustainability and depreciation of the irrigation and water abstraction, industrial effluents (indus- natural capital stock. trialisation), agricultural runoff, domestic wastes (urbanisa- Response: action taken at a political and/or management level tion), navigation and dredging, sea-level rise induced by land- that can include scientific responses (research efforts, moni- based activities or groundwater abstraction affecting the toring programs) as well as policy and/or management re- coastal zone (e.g., decrease of riverine sediment load leading sponse to either protect against changes, such as increased to instability of coastal geomorphology) and other forcing nutrient or contaminant input, secondary sea-level rise, or to functions, such as climate change. ameliorate and/or rehabilitate adverse effects and ensure or State and state change: the indicator functions and how they re-establish the chance for sustainable use of the system’s re- are affected, for example: water, nutrient and sediment trans- sources. Fig. 4.4. LOICZ-Basins. Schema of assessment tables 2. characterisation and ranking of the various issues of individual catchment scale) and the literature references change, based on either qualitative (i.e., expert judge- can be found in the individual reports (see www.loicz.org ment) or quantitative (data) information. This step and Appendix A.1). includes identification of critical load and threshold In this chapter we summarise and focus on the re- information for system functioning where available gional and sub-regional scales. The regional-continental (e.g., Kjerfve et al. 2002, Lacerda et al. 2002, Gordeev results are discussed in the main text; individual assess- et al. 2005). ments of catchment basins can be found in the LOICZ- Basins reports (see Appendix A.1). The upscaling to sub- Thus, LOICZ-Basins provides a typology of the cur- regions and sub-continental or continental scale is illus- rent state and expected trends of coastal change under trated in partly coloured tables where green, yellow and land-based human forcing and natural influences. The red indicate the sequence of increased ranking of im- assessment follows a set of key questions that cover the portance

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