RESUMO
Greenhouse gases (GHG) have extensive environmental effects by trapping heat and causing climate change and air pollution. Land plays a key role in the global cycles of GHG (i.e., carbon dioxide (CO2), methane (CH4), and nitrogen oxide (N2O)), and land use change (LUC) can lead to the release of such gases into the atmosphere or the removal of them from the atmosphere. One of the most common forms of LUC is agricultural land conversion (ALC) where agricultural lands are converted for other uses. This study aimed to review 51 original papers from 1990 to 2020 that investigate the contribution of ALC to GHG emissions from a spatiotemporal perspective using a meta-analysis method. The results of spatiotemporal effects on GHG emissions showed that the effects were significant. The emissions were affected by different continent regions representing the spatial effects. The most significant spatial effect was relevant to African and Asian countries. In addition, the quadratic relationship between ALC and GHG emissions had the highest significant coefficients, showing an upward concave curve. Therefore, increasing ALC to more than 8 % of available land led to increasing GHG emissions during the economic development process. The implications of the current study are important for policymakers from two perspectives. First, to achieve sustainable economic development, policymaking should prevent the conversion of more than 90 % of agricultural land to other uses based on the turning point of the second model. Second, policies to control global GHG emissions should take into account spatial effects (e.g., continental Africa and Asia), which show the highest contribution to GHG emissions.
RESUMO
This research used a qualitative and quantitative approach to classify factors influencing wheat farmers' social, economic, and environmental vulnerability in Khorasan Razavi province, Iran, from the perspective of elite wheat farmers and agricultural specialists, and then to establish some recommendations based on the results. To achieve the study objectives, in the qualitative part, in-depth interviews were held with 20 agricultural specialists in the field of wheat cultivation, and 9 elite wheat farmers were selected using a purposive sampling method. Using stratified random sampling, 391 wheat farmers participated in the quantitative part. From the agricultural specialists' viewpoint, the prime factor affecting vulnerability was the social factor "farm management". The second factor was the environmental vulnerability factor "Sunn pest and heat", and the final factor was the economic vulnerability factor "the costs of fertilizer, equipment, and machines and their maintenance". In contrast, from the viewpoint of elite wheat farmers, the dominant factor affecting vulnerability was the economic factor "the costs of equipment, fertilizer, and machines and their maintenance". Regarding social vulnerability, "Governmental support" was stressed and the most important environmental vulnerability factor was "Sunn pest and cold". The results of confirmatory factor analysis were more in line with the views of agricultural specialists. According to the results, it is suggested that the agricultural extension system provides timely training to farmers in order to properly manage farms in times of crisis. The government should also compensate part of the costs of social and economic damage to farmers by providing free or low-interest loans.
