Does asymmetric birch effect phenomenon matter for environmental sustainability of agriculture in Tunisia?

This paper investigates the validity of the Environmental Kuznets Curve (EKC) hypotheses for agriculture. The impact of precipitations on soil CO2 emissions is incorporated in the EKC hypothesis to assess the so-called “Birch effect phenomenon.” Through an autoregressive distributed lag (ARDL) bound test modeling and using annual data from 1975 to 2014, we examine the short- and long-term relationships between net agricultural values added per rural capita, energy consumption, precipitation and agricultural CO2 emissions in Tunisian agriculture. We then used the nonlinear version of ARDL (NARDL) to examine the asymmetric effect of precipitations on CO2 emissions. The EKC assumption is validated in favor of the agricultural sector in both short and long-run associations, suggesting the adoption of cleaner production practices. The results also indicate that precipitation increases soil CO2 emissions in the short-term as well as in the long-term, confirming the Birch effect phenomenon and reflecting the specificity of the Tunisian climate-ecosystem. The asymmetric findings provide evidence of different CO2 emissions response to negative and positive shocks of precipitations in terms of magnitude, whereas the energy use in agriculture is found not to affect CO2 emissions when switching from linear to a nonlinear model. As recommendations, promoting the agricultural productivity and preserving farmland in Tunisia should be among the main actions for any agricultural policy to improve economic growth and to achieve environmental sustainability.