SMOKE ON WATER
Threats – Peatlands under pressure While peatlands are under pressure from a range of human activities, drainage is the immediate and most wide-ranging global threat to the integrity of these ecosystems. Humans have long exploited the world’s peatlands with over 65 million hectares estimated to have been affected by our activity (Joosten et al., 2012). We have taken peatlands for granted, often seeing as them unproductive or even hostile land to be drained when desired for human use. Records dating back as far as the eighth century show that large-scale drainage for agricultural purposes occurred in the Netherlands.
In China, peatland drainage for agricultural expansion started around 200 years ago, and almost all peatlands have been degraded by crop production or grazing (Joosten et al., 2012). Large-scale land-use change in tropical peatlands only started during the mid-twentieth century and large areas remain undisturbed (Parish et al., 2008; FAO, 2014; Dargie et al., 2017). In South America and Central Africa, the expansion of road networks followed by commercial agriculture or forestry appears to be an emerging threat for the largely undisturbed tropical peatlands (Dargie et al., 2017; Roucoux et al., 2017). This would follow the pattern seen in Southeast Asia where peat swamp forests have been targeted for agricultural expansion mainly for palm oil and forestry projects, for pulp wood production and relocation programmes (Hooijer et al., 2010, 2015; FAO, 2014). Over 90 percent of peat swamp forests in western Southeast Asia have been disturbed (Miettinen et al., 2017). In the past 30 years, substantial drainage in both Malaysia and Indonesia has been undertaken to allow plantation development, driven by the demand for palm oil, timber and paper (Miettinen et al., 2017; FAO, 2014). In Indonesia, an additional factor is that population growth and urbanization have increased demand for new agricultural land (FAO, 2014). Much peatland conversion resulted from a national programme for relocating millions of landless people (FAO, 2014), which ended in 2015. The typical approach by these new small landholders has been to use fire to clear land and temporarily boost its fertility. Fire is also widely used in commercial agriculture. Commercial forestry Commercial forestry, which is prevalent across Scandinavia, North America, the countries of the former Soviet Union, the United Kingdom, and Southeast Asia, is the second greatest cause of land-use change in peatlands (Parish et al., 2008; Joosten et al., 2012). Globally, commercial forestry has claimed more than 120,000 km 2 of peatlands, mainly within boreal and temperate regions where the land is drained to
We now have a better understanding of the huge impacts of peatland drainage on carbon storage, water regulation, biodiversity conservation and other ecosystem services, and the resulting economic, environmental and social costs. As well as having “nearly irreversible” effects on peat structure and the ecological services peatlands provide (Oleszuczuk et al., 2008), draining peatlands substantially increases fire risk and can lead to significant loss of soil productivity and even land loss through subsidence. Drainage for agriculture Agricultural expansion has been the main driver of change in peatlands around the world (Joosten & Clarke, 2002). Peat soils need to be drained to make them cultivable and this releases nutrients in the short term. However, the soil can rapidly oxidise, dry and degrade leading to low fertility and ultimately low productivity (FAO, 2014). Drainage may involve ditches or larger canals, and gullies that form spontaneously in mountain peatlands (Evans et al., 2005). Where peatland drainage has resulted in soil degradation, yield reductions have led to the abandonment of large areas (FAO, 2014). Nowadays, there is very little new peatland drainage in boreal and temperate zones (Rieley, 2014) due to declines in crop production and increasing costs (Parish et al., 2008; Hooijer et al., 2012, 2015). However, the area being drained in the tropics is dramatically increasing with Southeast Asia leading the way. Europe has seen the greatest area of peatland drainage of any continent (Parish et al., 2008). Hungary, Greece, the Netherlands and Germany were among the top European countries reporting the use of drained peatlands for agriculture (Joosten & Clarke, 2002). An estimated 38,600 km 2 have been drained for agriculture in the former Soviet Union (Inisheva, 2005; FAO, 2014). Large areas rendered unproductive have now been abandoned and are susceptible to fires in dry summers. Peatlands in North America have been used to grow cranberries, vegetables, sugar cane, rice and fodder (Joosten, 2002) but they have been less affected by drainage (Joosten, 2010).
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