ECOSYSTEM RESTORATION FOR CLIMATE CHANGE MITIGATION
All living matter (biomass) – from grasses and trees to salt marshes and plankton – stores carbon. Terrestrial biomass carbon stores are often referred to as “green carbon”. Worldwide, terrestrial vegetation, soil and detritus currently store 2261 Gigatonnes of carbon (GtC; IPCC, 2007)1. Approximately half of terrestrial biomass carbon stocks are found in forest (IPCC, 2007). The oceans and coastal vegetation also store a large amount of carbon (often known as “blue carbon”), which is thought to be approxi- mately 38334 GtC (IPCC, 2007), though there is uncertainty about the precise quantity
(Nellemann et al., 2009).
Much recent attention has been given to the potential of eco- systems, especially forests, to take up (sequester) additional carbon and hence mitigate climate change. Unfortunately, this process is disrupted when natural ecosystems are converted for agricultural use. This releases much of the carbon stored in plants and soil, and also alters the physical and biological ef- fects of the landscape on the climate (Bala et al., 2007).
Some of these effects warm the climate, whilst others cool it. The high albedo (reflectivity) of grassland and deserts plays a role in atmospheric cooling (Hansen et al., 1998; Thompson, 1998). High rates of evapotranspiration (release of water into the atmosphere) from tropical forest reduce surface air tem- perature and increase rainfall (Bonan, 2008). The structure of vegetation also influences the regional climate: for example, a study in Australia found that land cover change (mainly defor-
1 To illustrate how substantial these ecosystem stores of carbon are, the global annual emissions of carbon dioxide from human activity in 2004 totalled 38 Gigatonnes (IPCC 2007).2 Services include provisioning (e.g. fish and minerals), regulating (e.g. role in climate), supporting (e.g. role in water cycle) and cultural (e.g. tourism, recreation)
estation) explained up to 50% of the observed warming and changes to rainfall patterns due to reduced surface roughness
(Pitman et al., 2004).
The marine environment also has a key role in climate regula- tion. The oceans store and conduct heat, while ocean chem- istry is important in regulating carbon uptake (IPCC, 2007;
Reid et al., 2009).
Restoration of terrestrial and marine ecosystems therefore protects and enhances the climate regulating services of eco- systems as well as the carbon stocks that aid climate change mitigation.
Many ecosystems are currently carbon sinks (they store more carbon than they lose). The IPCC Fourth Assessment (AR4) Report suggests that the size of the terrestrial sink is approxi- mately 0.5–1.5 GtC per year while the marine sink is approxi- mately 1.8–2.6 GtC per year (IPCC, 2007). However, land use change and degradation damage the terrestrial sink as well as generating carbon emissions (Ong, 1993; Anser et al., 2005; Eliasch, 2008; Lal, 2008).
59
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112