Resilience and Alternative Stable States of Tropical Forest Landscapes under Shifting Cultivation Regimes

Abstract

Shifting cultivation is a traditional agricultural practice in most tropical regions of the world and has the potential to provide for human livelihoods while hosting substantial biodiversity. Little is known about the resilience of shifting cultivation to increasing agricultural demands on the landscape or to unexpected disturbances. To investigate these issues, we develop a simple social-ecological model and implement it with literature-derived ecological parameters for six shifting cultivation landscapes from three continents. Analyzing the model with the tools of dynamical systems analysis, we show that such landscapes exhibit two stable states, one characterized by high forest cover and agricultural productivity, and another with much lower values of these traits. For some combinations of agricultural pressure and ecological parameters both of these states can potentially exist, and the actual state of the forest depends critically on its historic state. In many cases, the landscapes’ ‘ecological resilience’, or amount of forest that could be destroyed without shifting out of the forested stability domain, declined substantially at lower levels of agricultural pressure than would lead to maximum productivity. A measure of ‘engineering resilience’, the recovery time from standardized disturbances, was independent of ecological resilience. These findings suggest that maximization of short-term agricultural output may have counterproductive impacts on the long-term productivity of shifting cultivation landscapes and the persistence of forested areas.

Conceptualising the Global Forest Response to Liana Proliferation

“…While subsequent data elements can be sampled by careful stratification, measurement of liana dominance may require cutting trials to adjust L:T ratios to ensure sufficient spread for determining the effect of variation on forest recovery. While experimental manipulations are often difficult in ecological systems (Magnuszewski et al, 2015), procedures for liana cutting trials are well-established (Estrada-Villegas and Schnitzer, 2018). Inclusion of controls with no manipulation (before-after controlimpact; Stewart-Oaten et al, 1986) across important driver gradients, will ensure that outcomes have arisen from liana competition rather than other positive feedbacks and drivers.…”

“…The consequence of exceeding these critical thresholds in forests has global significance, because these ecosystems sustain global biodiversity (Gibson et al, 2011), carbon sequestration (Pan et al, 2011) and national economies (Carrasco et al, 2014). Resilience thresholds in forests may be exceeded in several ways: conversion to treeless or alternative forest states by fire, drought, pests and grazing (Chapin et al, 2004;Malhi et al, 2009;Hirota et al, 2011;Hoffmann et al, 2012) and potentially climate change (Scheffer et al, 2012); reduced stand growth with over-harvesting of timber Bahamondez and Thompson, 2016); increasing biomass with rising CO 2 (Higgins and Scheiter, 2012); declining forest cover with shifting agriculture (Magnuszewski et al, 2015); and more positively, increasing biodiversity with plant biomass recovery following disturbance (Lennox et al, 2018). However, identification of thresholds requires extensive spatial and temporal data to diagnose true state changes resulting from exceeding a threshold, versus abrupt changes in state resulting from abrupt changes in environmental influences (Ratajczak et al, 2018) (see glossary, Table 1).…”

Simple Incentives and Group Dependence for Successful Payments for Ecosystem Services Programs: Evidence from an Experimental Game in Rural Lao PDR

“…Its practitioners are frequently disadvantaged minority peoples with traditional resource rights recognized by themselves and their neighbors, but not always by governments (Fox et al 2009;Padoch et al 2007;Kenney-Lazar 2013). Swidden is often misrepresented as unproductive (Fox et al 2009), and conflated with poverty and deforestation, in spite of growing evidence that dynamic agroforest mosaics provide environmental services, forest products, and biodiversity habitat (Rerkasem et al 2009, Bruun et al 2013Magnuszewski et al 2015). Shifting cultivation has unique complexities among PES-targeted systems.…”

Ecological outcomes and livelihood benefits of community‐managed agroforests and second growth forests in Southeast Brazil

“…, Magnuszewski et al . ). Strengthening community management systems may therefore be a vital key to sustain increasing and permanent levels of tree cover in tropical regions.…”