The fundamental reason for the presence of peatlands is a positive balance between plant production and decomposition of organic matter. Organic matter accumulates in these systems because prolonged waterlogged conditions result in soil anoxia (i.e. exclusion of oxygen), and under these conditions decomposition rates can be lower than those of primary production, as seen in Figure 8.1. Climate therefore plays an important role in peat accumulation, both directly by affecting plant productivity and decomposition of organic matter, and indirectly through its effects on hydrology, water balance and vegetation composition (for a summary, refer to Yu, Beilman and Jones (2009)). Climate provides broad-scale controls on peatland extent, types and vegetation, and ultimately, ecosystem services such as carbon sequestration and storage, as well as water and hazard regulation (Chapters 4 and 5). Peatlands can therefore play a vital role in ecosystem-based adaptation in helping society mitigate and adapt to climate change.
Future climate change is likely to alter the hydrology and soil temperature of peatlands, with far-reaching consequences for their biodiversity, ecology and biogeochemistry, and interactions with the Earth system. For example, the possibility of drier conditions allowing peat erosion and increases in CO2 emissions that would result in a positive feedback to climate change (Turetsky 2010). Peatlands that have been damaged by human activity are more vulnerable to climate-induced changes in hydrology and temperature, but suitable management strategies may make them more resilient to changes and help to stabilise the delivery of ecosystem services (Chapter 1).
This chapter describes the interactions between climate and peatlands in three sections. The first section explains how present climate influences peatlands, by documenting how climate limits peatland geographical extent globally, and how bioclimatic envelope models can predict peatland extent. We indicate how each type of peatland is linked to a specific climate range, and introduce the concept of how climate controls peatland ecosystem function and services. The second section looks into the past. It describes how peat preserves a record of past climates and environmental conditions that can be deciphered to reveal the history of peatland vegetation, hydrology and carbon accumulation changes in relation to past changes in climate. We highlight lessons that can be learned from the palaeo-record preserved in peat.