6.4.2.2 Agriculture, forestry and fisheries
Climate change is expected to have impacts on agriculture and, to a lesser extent, on forestry, although non-climatic factors, such as technological development and management practices can be more significant (Easterling, 2003). Climate variability and change also impacts fisheries in coastal and estuarine waters (Daufresne et al., 2003; Genner et al., 2004), although non-climatic factors, such as overfishing and habitat loss and degradation, are already responsible for reducing fish stocks. Globally an increased agricultural production potential due to climate change and CO2 fertilisation should in principle add to food security, but the impacts on the coastal areas may differ regionally and locally. For example, in Europe, climate-related increases in crop yields are expected in the north, while the largest reductions are expected in the Mediterranean, the south-west Balkans and southern Russia (Maracchi et al., 2005).
Temperature increases can shorten growing cycles, e.g., those of cotton and mango on the north coast of Peru during the El Niño (see Chapter 13, Section 13.2.2). More frequent extreme climate events during specific crop development stages, together with higher rainfall intensity and longer dry spells, may impact negatively on crop yields (Olesen et al., 2006). Cyclone landfalls causing floods and destruction have negative impacts on coastal areas, e.g., on coconuts in India (see Chapter 5, Section 5.4.4), or on sugar cane and bananas in Queensland (Cyclone Larry in March 2006). Rising sea level has negative impacts on coastal agriculture. Detailed modelling of inundation implies significant changes to the number of rice crops possible in the Mekong delta under 20-40 cm of relative sea-level rise (Wassmann et al., 2004). Rising sea level potentially threatens inundation and soil salinisation of palm oil and coconuts in Benin and Côte d’Ivoire (see Chapter 9, Section 9.4.6) and mangoes, cashew nuts and coconuts in Kenya (Republic of Kenya, 2002).
Coastal forestry is little studied, but forests are easily affected by climatic perturbations, and severe storms can cause extensive losses, e.g., Hurricane Katrina. Plantation forests (mainly P. radiata) on the east coast of North Island, New Zealand, are likely to experience growth reductions under projected rainfall decreases (Ministry for the Environment, 2001). Increasing salinity and greater frequency of flooding due to sea-level rise reduces the ability of trees to generate, including mangroves which will also experience other changes (Section 6.4.1.4) (IUCN, 2003).
Future climate change impacts will be greater on coastal than on pelagic species, and for temperate endemics than for tropical species (see Chapter 11, Section 11.4.6). For Europe, regional climate warming has influenced northerly migration of fish species, e.g., sardines and anchovies in the North Sea (Brander et al., 2003a). The biotic communities and productivity of coastal lagoons may experience a variety of changes, depending on the changes in wetland area, freshwater flows and salt intrusion which affect the species. Intensification of ENSO events and increases in SST, wind stress, hypoxia (shortage of oxygen) and the deepening of the thermocline will reduce spawning areas and catches of anchovy off Peru (see Chapter 13, Table 13.7). There is also concern that climate change may affect the abundance and distribution of pathogens and HABs, with implications for aquatic organisms and human health (Section 6.4.2.4). The linkage between temperature changes and HABs is still not robust, and the extent to which coastal eutrophication will be affected by future climate variability will vary with local physical environmental conditions and current eutrophication status (Justic et al., 2005). Ocean acidification is a concern, but impacts are uncertain (Royal Society, 2005). Climate change also has implications for mariculture but again these are not well understood.