Terrestrial Ecosystems
The progress made in the study of C emissions and mitigation strategies, the role of soil in the C dynamic and in the measurement of storage and flows of C in the terrestrial ecosystems of Mexico were subject to study. A model of C collection and emissions, recommended by the IPCC (1996), was used for national and regional analysis. The analysis units used were: the INEGIS’s eco-regions, the vegetation units proposed by Rzedowski and the types of soil (series 1, INEGI). According to the national inventory of greenhouse gas emissions (INE 2000), the sectors releasing the most CO2 into the air at the national level are transport and energy (60%) and the forestry sector (35%). Within the forestry sector, the main factors leading to C emissions are change in soil usage, especially that related to deforestation. The annual rate of deforestation has increased significantly as the national average passed from 0.36% (1977-1993) to 0.73% (1993-2000) over a 10-year period. However, emissions are different in each ecosystem, for instance tropical forests amount for 76% of emissions in this sector, while temperate forests for only 12 %. Currently, estimates of CO2 emissions at the national level are being updated with the data obtained from the last National Forestry Inventory based on both the spatial information and the biomass. In addition, there is also an estimate of the area that could be used for different mitigation strategies, as well as an estimate concerning the collection of associated C, since the management of natural forests and of protected natural areas is of the greatest importance.
The analysis also included the measurement of organic carbon in the soil (OCS, in percentage terms) at the national level (9,500 profiles). There is also a map of the OCS (0-30 cm) related to soil units (recognized by INEGI) and the OCS associated with 16 vegetation systems, to which the INEGI information concerning the country’s types of vegetation was added. There was data concerning the size of carbon storage in the aerial and subterranean parts of the forest systems [tropical (caducifolia forests, sub-caducifolia forests and rainforests), temperate (primary and secondary), and brushwood] and selected agriculture, as well as preliminary values for CO2 emissions coming from various natural vegetation and agricultural cultivation systems (traditional and improved). Nevertheless, there are only a few published works addressing the issue of carbon measurement in the ecosystems major carbon stores (just four articles), therefore it is important to encourage this type of work because such articles form the basis for further estimates at the regional and national levels. Finally, there was a case study case addressing internal carbon flows which highlighted that the inter-annual variability of data is high. In conclusion, the Terrestrial Ecosystems Group presented a list of challenges facing its members and the tasks that remain pending. (Annex 5).
