RESUMEN
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.
RESUMEN
Land consolidation (LC) is a widespread form of rural planning and is often presented as an important tool for mitigating land degradation. We therefore decided to make a systematic review of the effects of LC projects implemented under different natural and socio-economic conditions. Our results show that there is a major dichotomy in the understanding of LC. Studies from some parts of the world, e.g., Africa and South-east Asia, mostly report on LC projects aimed principally at creating larger fields to facilitate management. Studies from other regions, notably from Europe and China, describe LC as a complex form of planning that includes various types of land management measures. The effects of LC projects on land degradation are strongly linked to the type of project. Within the sample of reviewed studies, the effect of LC projects on land degradation was ambivalent, and projects not including land management measures even tended to contribute to land degradation. Conversely, in studies where LC projects involved specific land management measures, LC had a positive effect on most land degradation types. The results of our study indicate that LC projects can help significantly to mitigate land degradation.
