INTEGRATED LAND-USE SYSTEMS - ASSESSMENT OF PROMISING AGROFOREST AND ALTERNATIVE LAND-USE PRACTICES TO ENHANCE CARBON CONSERVATION AND SEQUESTRATION

Degraded or sub-standard soils and marginal lands occupy a significant proportion of boreal, temperate and tropical biomes. Management of th ese lands with a wide range of existing, site-specific, integrated, ag roforest systems represents a significant global opportunity to reduce the accumulation of greenhouse gases in the atmosphere. Establishment of extensive agricultural, agroforest, and alternative land-use syste ms on marginal or degraded lands could sequester 0.82-2.2 Pg carbon (C ) per year, globally, over a 50-year time-frame. Moreover, slowing soi l degradation by alternative grassland management and by impeding dese rtification could conserve up to 0.5-1.5 Pg C annually, A global analy sis of biologic and economic data from 94 nations representing diverse climatic and edaphic conditions reveals a range of integrated land-us e systems which could be used to establish and manage vegetation on ma rginal or degraded lands. Promising land-use systems and practices ide ntified to conserve and temporarily store C include agroforestry syste ms, fuelwood and fiber plantations, bioreserves, intercropping systems , and shelterbelts/windbreaks. For example, successful establishment o f low-intensity agroforestry systems can store up to 70 Mg C/ha in bor eal, temperate and tropical ecoregions. The mean initial cost of soil rehabilitation and revegetation ranges from $500-3,000/ha for the 94 n ations surveyed. Natural regeneration of woody vegetation or agro-affo restation establishment costs were less than $1000/ha in temperate and tropical regions. The costs of C sequestration in soil and vegetation systems range from $1-69/Mg C, which compares favorably with other op tions to reduce greenhouse gas emissions to the atmosphere. Although a groforestry system projects were recently established to conserve and sequester C in Guatemala and Malaysia, constraints to wide-spread impl ementation include social conditions (demographic factors, land tenure issues, market conditions, lack of infrastructure), economic obstacle s (difficulty of demonstrating benefits of alternative systems, capita l requirements, lack of financial incentives) and, ecologic considerat ions (limited knowledge of impacts and sustainability of some systems) .