Environmental and economic impacts of agri-environmental schemes designed in French West Indies to enhance soil C sequestration and reduce pollution risks. A modelling approach

Abstract

Agri-environmental schemes (AESs) are the main public policy instrument used in Europe to encourage farmers to adopt environmentally-friendly farming practises. Some AESs designed in French West Indies to replace N fertilizers with composts to reduce nitrate pollution and enhance C sequestration have been unsuccessful because few farmers adopted them despite the subsidies offered for the provision of environmental benefits. To explain this low adoption rate, we assessed the agri-environmental and economic impacts of two AESs and compare them with the most widely-applied strategy based on inorganic N fertilizer (NFER), and with an organic strategy based on sewage sludge (SLUD), a free organic amendment. The first AES was proposed in 2007 (AES old) and only concerned with the use of composts. The second was proposed in 2014 (AES new) and combines the use of composts and inorganic N fertilizer at a rate 25% lower than NFER. The study was applied to water yam using a crop model to obtain agri-environmental indicators over a period of ten years, which were then used to calculate economic outputs for small and large farms. Although AES old increased C sequestration by 300% and reduced nitrate leaching by 80% compared to NFER, it also reduced yields (13%) and net income for farmers (30%). The subsidy offered by AES old did not compensate the loss of productivity, which explains its low rate of adoption. AES new and SLUD increased C sequestration (350% and 400%) and reduced nitrate leaching (45% and 34%), and maintained yields and net income after five years of implementation. Yields and net income during the first five years were 5-10% lower than under NFER. Although the land area concerned by SLUD is limited because of regulatory constraints, AES new could be a satisfactory policy instrument in French West Indies because it promotes environmental benefits and maintains economic income in the medium term for smallholder using family labour. The economic performance of AESs was lower for large farms; the adoption rate could be improved for these farmers through the implementation of mechanization to reduce labour costs. For both farm types, it may be necessary to increase subsidies during the first five years to offset yield losses during this period and the fixed and transition costs attached to adoption.

A novel approach for assessing the contribution of agricultural systems to the sustainable development of regions with multi-scale indicators: Application to Guadeloupe

“…The cropping system characteristics required to improve the contribution of agriculture to sustainable development may help to identify relevant economic incentives, such as agrienvironmental schemes that would encourage farmers to adopt environmentally-friendly farming practices such as reducing the impact of pesticides on water bodies. Examples of such incentives already exist in the French West Indies, such as that which has been prototyped to favour the adoption of composts to enhance carbon sequestration in yam-based cropping systems (Blazy et al, 2015). Direct or indirect subsidies are important drivers of changes to practices because fixed and transaction costs are key drivers for the adoption of new cropping systems (Barreiro-Hurlé et al, 2010).…”

Designing scenarios for upscaling climate-smart agriculture on a small tropical island

“…A recently conducted GHG inventory analysis indicated that N fertilizers and lime spreading were key causes of GHG emissions (Colomb et al, 2014). Replacement of inorganic fertilizers with organic amendments in agriculture has been explored as a means of managing soil fertility in a more sustainable manner (Blazy et al, 2015;Sierra et al, 2016). This situation is particularly critical, as the combination of climate change and intensive agricultural practices may lead to a decrease in soil organic matter content and thus an increase in CO2 emissions (Sierra et al, 2015).…”

Perceptions of Smallholder Farmers towards Organic Farming in South Africa

“…In some studies conducted in developed and developing countries, the results revealed that traditional supply-based policies alone may unlikely guarantee an appropriate technological innovation level by farmers [15]. For instance, in most tropical countries, failures recorded in compositing aroused from the dearth of attention paid in the planning stage to understand the demand, economic and technical aspects involved in organic farming methods [16,17].…”