Essential Climate Variables GTOS 67

BIOMASS

T12 Assessment of the status
of the development of the standards for the
Terrestrial Essential Climate Variables

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS (FAO)
Rome, 2009

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ABSTRACT

The importance of biomass as an Essential Climate Variable is due to both its role as a carbon sink during the process of photosynthesis, its role in governing ecosystem productivity and its growing use for generation of bioenergy. Sustainable management of biomass sources, in particular forests, which store most of the Earth’s biomass, contributes to reduction of CO2 in the atmosphere, mitigation of climate change and protection of other ecosystem services including biodiversity conservation and water resources. Estimates of biomass change (due to land use and management practices or natural processes) enable a direct measurement of carbon sequestration or loss (as long as associated changes in soil carbon are accounted for) that can help validate carbon-cycle models and to quantify the human induced impacts on global climate change. Carbon emission from deforestation is the largest source of greenhouse gas emissions in many developing countries.

Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD) in Developing Countries could potentially achieve a reduction of 50 Gt of carbon until 2100 (Gullison et al. 2007). Within the circumpolar boreal, fire represents an important source of carbon emissions due to its alteration of biomass carbon stocks (Isaev et al. 2002; Turquety et al. 2007), although uncertainties remain on the share of C that is stored in stable forms (e.g. charcoal) during ignition of biomass and of soil organic matter (SOM). In addition to fire, other disturbance and natural hazards, such as large insect outbreaks, can also result in a transition of a forest from carbon sink to source. This suggests that future efforts to influence the carbon balance through forest management should consider also natural or anthropic disturbances (Kurz et al. 2008).

This document is mainly related to living terrestrial above-ground vegetation biomass, especially woody biomass. The below-ground component is still poorly known, because it can not be detected by remote observations and it needs labour- and time-intensive in situ measurements.