Climate Change 2001: Mitigation

4.2.2 Land Use in the Temperate and Boreal Zones

4.2.2.1 Historical and Present Land Use in the Temperate and Boreal Zones

The temperate zone is the most populated zone of the world, while the boreal zone is quite sparsely populated. For thousands of years forest area has diminished, particularly in the temperate zone, as forests were cleared for agriculture and pasture. Clearing of the European Mediterranean region began ca 5000 years ago; in Central Europe and in China deforestation occurred in early Medieval times; in parts of Russia and Mongolia forest clearing occurred in late Medieval times; and in North America clearing occurred mainly in the 19th century (Mather, 1990, see Figure 4.4). Since the mid 20th century the net forest area of the temperate zone has no longer decreased but has instead increased (Kauppi et al., 1992). The inner parts of the boreal zone in Siberia, Alaska, and Canada have not been subject to significant land-use management. The opportunities present to store carbon in terrestrial ecosystems in the boreal and temperate zones are thus very much determined by historical land-use change and the associated losses of carbon (Kurz and Apps, 1999).

Table 4.2: Overview of biological carbon mitigation issues and opportunities in selected countries/regions (Based, in part, on Sedjo and Lyon, 1990; Fujimori, 1997; Nilsson and Shvidenko, 1998; De Camino et al., 1999; Sohngen et al., 1999; Zhang, 1996)

Region	Issues	Options to store carbon arising from the issues

USA/Canada	Primary forest based forestry and second rotation forestry High tech forest industry Fierce environmental debates Large impacts of natural disturbances Agriculture under pressure that restore soil C (excess agricultural land)	Fire management Afforestation Efficient use of wood products Bioenergy Farming practices (e.g., reduced tillage)

Europe	Agriculture under pressure, afforestation of agricultural lands Changing ownership Forest health problems Move towards nature-oriented forest management High tech forest industry In eastern Europe, privatization of forest ownership that restore soil C	Nature-oriented forest management Nature reserves Afforestation Efficient use of wood products Bioenergy Farming practices (e.g., reduced tillage)

Russia	Transition to market economy Bad financial situation of forest service Large impacts of natural disturbances Low levels of fellings	Natural regeneration on abandoned agricultural land Fire management Capacity building Farming practices that restore soil C

Japan	Plantation-based forestry and managed secondary forestry High tech forest industry Forest health problems Move towards nature-oriented management	Efficient use of wood Nature-oriented forests Reserves Bioenergy

China	Transition to market economy Transition from non-wood fibre sources to using wood fibre Floods resulting from loss of forest	Afforestation with plantations Protecting primary forests Flood protection Farming practices (e.g., reduced tillage) that restore soil C

Australia/ New Zealand	Plantation-based forestry and some primary forest based forestry High tech forest industry Afforestation of agricultural lands	Fire management Afforestation with plantations Efficient use of wood products Bioenergy Halting deforestation Farming practices (e.g., more forages) that enhance soil C

Argentina, Chile, Brazil	Plantation-based forestry and some primary forest based forestry High tech forest industry developing Plantations are not able to reduce deforestation because they provide different set of products	Afforestation with plantations Efficient use of wood products Bioenergy Halting deforestation Farming practices (e.g., reduced tillage) that and services. enhance soil C

Mexico	Forestry largely based on native forests Large deforestation rates Economic incentives favour agriculture/cattle over forestry Afforestation of degraded lands mostly for restoration	Halting deforestation Sustainable forest management of native forests Social forestry Afforestation with local species Bioenergy

Understanding the historic and current net sink of C in the temperate and boreal zones is important to assessing the potential of present and future management options. In general, estimates of C flows have been based on a variety of methods and data, resulting in a wide range of reported values for C flows per region. The confidence level in each separate value is therefore low. For example, for European forests the estimates of the present C sink vary from almost 0 to 0.5 GtC/yr (Nabuurs et al., 1997; Martin et al., 1998; Valentini et al., 2000; Schulze, 2000). For Canada, early estimates, based on a static assessment, indicated a net sink of 0.08GtC/yr for the mid-1970s (Kurz et al., 1992); whereas subsequent analyses, accounting for changes in forest disturbances over time (see section 4.2.3), indicated that Canadian forests became a small net source of C (–0.068GtC/yr) by the early 1990s (Kurz and Apps, 1999). Estimates of carbon accumulation in woody biomass for the USA also show a large uncertainty. While the average rate for the USA C sink ranges from 0.020 to 0.098GtC/yr for the 1980s and 1990s (Birdsey and Heath, 1995; Turner et al., 1995; Houghton et al., 1999), atmospheric inversion models applied to the North American continent suggest a sink of 1.7 ± 0.5GtC/yr, largely south of 51ºN (Fan et al., 1998), but with very low levels of confidence (Bolin et al., 2000).

In the less intensively managed forests of Russia and Canada, changes in mortality associated with natural disturbances appear to dominate over management influences (see Section 4.2.4). In European Russia, managed forest ecosystems were estimated to be a sink of 0.051GtC/yr between 1983 and 1992, but the less actively managed Siberian forest was a net source of 0.081–0.12GtC/yr (Shepashenko et al., 1998). The available estimates for Siberia differ even more than for the other regions mentioned above, and their confidence level may be “low” (Schulze et al., 1999).

Recent FAO statistics on 55 countries in the temperate and boreal zones indicate a general increase in the forest carbon stock (trees only) of 0.88GtC/yr (UN-ECE/FAO, 2000). Changes in forest management and changes in the environment have contributed to this trend. In Europe, the trend is consistent with the observation of increased growth in individual stands noted by Spiecker et al. (1996). The FAO statistics indicate that between the 1980s and 1990s both net annual increment and timber fellings increased, but that the rate of change was lower for fellings than for growth, resulting in a substantial increase in the carbon sink from the 1980s to the 1990s (Kuusela, 1994; Kauppi et al., 1992; Sedjo, 1992; Dixon et al., 1994; UN-ECE/FAO, 2000). The carbon sink in live woody vegetation was on the order of 10% of the fossil fuel CO₂ emissions in the USA and in western Europe, and higher in the 1990s than in the 1980s (c.f. Kauppi et al., 1992).

These relatively high sequestration rates are not a result of active policies aimed at climate mitigation, but less rather appear to be related to general trends in land use and land-use change. In the USA, Schimel et al. (2000) and Houghton et al. (1999) estimate that the observed sink is a result mainly of changes in land use and land management, rather than a response to changes in the environment. The latest observations, based on forest inventory data (UN-ECE/FAO, 2000), are reflected in the Special Report on LULUCF (IPCC, 2000a). The IPCC (2000a) estimates that the total global terrestrial biopheric sink in the 1990s amounted to 0.7GtC/yr, despite a source from land-use change in the tropics of 0.9GtC/yr.

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