Reorienting paradoxical land use policies towards coherence: A self-adaptive ensemble learning geo-simulation of tea expansion under different scenarios in subtropical China

The expansion of cash crops has raised contradicting interests between two bureaucratic bodies (the economy-oriented one that advocates cash crop production and the conservation-oriented one that focuses on natural resources protection) in many places around the world. Recent past has saw growing efforts on the theoretical linkages between cash crop production and conservation, but the solutions to the cash cropping −related land use conflicts remain as violent controversy. Using a geo-simulation approach, this paper models the tea expansion under different policy scenarios and evaluates the effectiveness of these policies in Anji County (China), as a contribution to the scientific basis for formulating sustainable cash cropping practices and alternative land use policies. In particular, a new self-adaptive cellular automaton model based on ensemble learning (EL-CA) is developed and three policy scenarios (economy-over-conservation (EOC), conversion-over-economy (COE), and economy-balance-conservation (EBC)) are set to predict the tea expansion patterns in 2025. Results show that the EL-CA model significantly outperforms the traditional CA models based on empirical statistics. We find that the tea expansion under the EOC scenario is much more intensive than that under the COE and EBC scenarios. The most outstanding ecological consequence of tea expansion is the occupation of forests. Employing an equivalent coefficient approach, we further quantify the trade-offs between economic incomes (from tea expansion) and ecological loss (due to ecosystem service value (ESV) declines) under the three policy scenarios. In the EOC scenario, the loss in ESV far exceeds the benefit of tea expansion. Net change of ESV is higher than that of economic return under the COE. The economic benefit is approximately equal to the ecological loss in the EBC scenario. The EBC should be a socially preferred scenario, since it leads to sustainable tea expansion and minimal ecological impacts. Though the EBC scenario is a desirable choice, how to enforce these policies is an important consideration. Given the complexity in the Chinese policy context, we finally propose several possible measures to promote the coherence of paradoxical policies involving the allocation of land for cash crop cultivation.