In this chapter, general distinctions (both physical and biological features) of major latitudinal and climatic zones are outlined, so the reader can appreciate the broad similarities and dramatic differences in coastal wetlands across the globe (Chapters 7 to 11). We also look at the phytogeographical variations found on different coasts of the same continent and explain why the tropical floras of Atlantic and Pacific regions often are different, even within the same latitudinal range.

Climate zones and coastal wetland ecosystems

On a worldwide basis, there are four broad latitudinal zones of tidal wetlands (Figure 1.1). These world coastal wetland zones are: arctic and subpolar marshes; temperate zone marshes; subtropical marshes and mangroves; and tropical mangrove swamps. Each of these major ecosystems comprises a set of biological components interacting with their physical environment and providing characteristic wetland services (Figure 6.1) These services are defined by the Ramsar Convention as ‘the benefits people obtain from ecosystems, including provisions (food and water), regulating functions (buffering from floods and storms), nutrient cycling, and cultural needs (recreation, spiritual, and esthetic qualities)’. The vital services for human wellbeing include water purification and nitrate detoxification, climate regulation through sequestering and releasing of carbon in the biosphere, and mitigation of climate-driven sea level rise and storminess, which can result in erosion and devastating coastal floods (Millennium Ecosystem Assessment, 2005). Barbier et al. (2011) provide further details of the quality of estuarine and coastal ecosystem services and they estimate the financial losses to be expected from elimination of these services.