The shifting cultivation cycle in the study area has been reducing from 10 years to five or six years over the last 10 to 15 years. Contrary to popular opinion, this has not led to increased emissions because the driving force behind the change is not population increase (i.e. not pressure on the land) but a combination of public policy (subsidies which inadvertently encourage farmers to circulate their land more quickly) and the fact that clearing fallows requires much more labour if they are left from more than five years.
With a downward relative trend in maize prices over the last decade, and given that labour is the constraining factor in traditional agriculture, farmers nowadays prefer short cycles (cutting mature fallow is very labour intensive). Since in this area there has not been an increase in numbers of farmers engaged in shifting cultivation, this shortening of fallows appears to have been accompanied by an increase in areas abandoned by agriculture, and these areas are increasing their carbon stocks. Biomass emissions per ton of maize produced in a shifting cultivation system are around 1.27 t C compared to 0.59 t C in permanent agriculture, but this does not take into account the much higher carbon inputs in permanent agriculture in the form of energy and agrochemicals.
This message is the fifth of 8 key messages from the WOTROMEX programme. The case study area is the Ayuquila Basin in western Jalisco, which is a REDD+ Early Action Area under the Mexican national strategy for REDD+. WOTROMEX is supported by the Netherlands Science for Global Development Programme (NWO-WOTRO) and has been carried out by CIGA-UNAM together with the University of Twente, the Netherlands