Settlements 81 Introduction

This Chapter provides methods for estimating carbon stock changes and greenhouse gas emissions and removals associated with changes in biomass, dead organic matter (DOM), and soil carbon on lands classified as settlements. Settlements are defined in Chapter 3 as including all developed land -- i.e., residential, transportation, commercial, and production (commercial, manufacturing) infrastructure of any size, unless it is already included under other land-use categories. The land-use category Settlements includes soils, herbaceous perennial vegetation such as turf grass and garden plants, trees in rural settlements, homestead gardens and urban areas. Examples of settlements include land along streets, in residential (rural and urban) and commercial lawns, in public and private gardens, in golf courses and athletic fields, and in parks, provided such land is functionally or administratively associated with particular cities, villages or other settlement types and is not accounted for in another land-use category. See Chapter 3 for area reporting guidelines and for definitions of the six land-use categories.

Roughly 2% of Earth's terrestrial surface is covered by urban areas which are home to over 3 billion people. Over half of the world population currently lives in cities; this number is projected to double within 50 years (Crane and Kinzig, 2005). In many regions, land classified as urban, based on population density or city boundaries, is just a subset of land that can be classified as settlements using the criteria described above. These areas of less-dense settlement may extend well beyond the officially-defined border of a city, and in many regions their areas are expanding quickly (Elvidge et al., 2004; Gallo et al., 2004; Theobald, 2004). In areas that are primarily rural, even if land uses are not changing quickly, land devoted to residential uses can occupy a significant portion of the landscape. Transitions of Forest Land, Cropland, and Grassland to Settlements can have important impacts on carbon stocks and fluxes (Imhoff et al., 2000; Milesi et al., 2003).

Vegetation management in settlements may result in gains, losses, or transfers of carbon amongst the relevant pools. For example, branches removed during pruning or turfgrass clippings (biomass losses) may be left on site (transfer to litter), disposed of as solid waste (transfer to waste), or burned (emitted). Emissions of the relevant greenhouse gases are accounted for in the appropriate sections of the present guidance. For example, Table 2.3 in Chapter 2, Volume 5 (Waste), includes wood/ yard waste in national-scale statistics describing the fate of municipal solid waste at the national scale. Biomass removed as fuelwood from trees in settlements and used as fuel is accounted for in the Energy Sector. The net effect of conversion or management leading to increment, on the one hand, or to loss (such as from burning and decay), on the other, determines the overall C balance in settlements.

Soils and DOM in Settlements Remaining Settlements or in Land Converted to Settlements may be sources or sinks of CO2, depending on previous land use, topsoil burial or removal during development, current management, particularly with respect to nutrient and water applications, and the type and amount of vegetation cover interspersed among roads, buildings and associated infrastructure (Goldman et al., 1995; Jo, 2002; Pouyat et al., 2002; Qian and Follett, 2002; Kaye et al., 2004; Kaye et al., 2005).

The 1996 IPCC Guidelines covered above-ground biomass in trees in rural settlements, but not other settlement categories and pools.

The 2006IPCC Guidelines differ from those in the GPG-LULUCF as follows:

• The discussion and detailed methodologies have been moved from the Appendix to the main text and considered as greenhouse gas emission source or removal sector;

• The discussion and methodologies have been expanded to include the five biomass pools described in Chapter 1;

• Tier 1 default methodologies are presented;

• Additional data appropriate for Tiers 2 and 3 have been published since the GPG-LULUCF and are included here; and

• An expanded discussion on developing and applying country-specific Tier 2 and Tier 3 methodologies and values is included, including methods to work with more detailed activity data.

The carbon pools estimated for Settlements are above-ground and below-ground biomass, DOM, and soils. Sections 8.2 and 8.3 respectively describe methodology to estimate changes in carbon stocks for Settlements Remaining Settlements, and to estimate carbon stocks on Land Converted to Settlements. The methodology in the second section is broadly applicable to Land Converted to Settlements from any other type of land.

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