Land use is regulated through various mixes of command-and-control interventions that directly affect land use via land use restrictions, and other public interventions that indirectly affect land use via agricultural, forestry, trade or macro-economic policies. More recently, coalitions of public and private actors have designed market-based and/or demand-led policy instruments to influence land use—e.g., eco-certification, geographical indications, commodity roundtables, moratoria, and payments for environmental services. These innovative instruments fall along a continuum of state involvement and interact with traditional public forms of land use regulation, leading to “hybrid” interventions. This article reviews emerging evidence on the effectiveness of the main instruments used to promote sustainable land use, and explores interactions between the new demand-led interventions and formal regulatory public policies. Although there are still insufficient rigorous studies evaluating the effectiveness of hybrid instruments, available evidence suggests some positive direct and indirect benefits. Hybrid instruments combine elements from both private and public regulatory systems, in innovative and effective ways. We propose a typology to characterize potential interactions between instruments that regulate land use. It links various types of interactions—i.e., complementarity, substitution, and antagonism—to the various stages of regulatory processes—i.e., agenda setting, implementation, and monitoring and enforcement. We give examples of governments endorsing certifications or using certification to support their own policies; governments creating enabling conditions for hybrid instruments to mature, allowing for wider adoption; and private instruments reinforcing public regulations or substituting for missing or weak governance. In some cases, governments, NGOs and corporations compete and may hinder each other's actions. With favourable institutional and governance contexts, well-designed hybrid public-private instruments can be effective. More systematic evaluation could boost the effectiveness of instruments and enhance synergistic interaction with traditional public land-use policy instruments to achieve incremental benefits as well as longer-term transformative outcomes in land-use protection.

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Effectiveness and synergies of policy instruments for land use governance in tropical regions

The Anthropocene is characterized as an epoch when human influence has begun to fundamentally alter many aspects of the Earth system and many of the planet’s biomes. Here, we review and synthesize our understanding of Anthropocene changes in tropical forests. Key facets include deforestation driven by agricultural expansion, timber and wood extraction, the loss of fauna that maintain critical ecological connections, the spread of fire, landscape fragmentation, the spread of second-growth forests, new species invasion and pathogen spread, increasing CO2, and climate change. The patterns of change are spatially heterogeneous, are often characterized by strong interactions among different drivers, can have both large-scale and remote effects, and can play out through ecological cascades over long timescales. As a consequence, most tropical forests are on a trajectory to becoming altered ecosystems, with the degree of alteration dependent on the intensity and duration of the current bottleneck of human-induced pressures. We highlight the importance of this understanding to develop the strategies necessary for shaping the transition of tropical forests through the early Anthropocene, as well as highlight the opportunities and challenges for the tropical forest science community in the coming decades.

https://www.annualreviews.org/doi/pdf/10.1146/annurev-environ-030713-155141

Tropical Forests in the Anthropocene

Vast expanses of tropical forests worldwide are being impacted by selective logging. We evaluate the environmental impacts of such logging and conclude that natural timber-production forests typically retain most of their biodiversity and associated ecosystem functions, as well as their carbon, climatic, and soil-hydrological ecosystem services. Unfortunately, the value of production forests is often overlooked, leaving them vulnerable to further degradation including post-logging clearing, fires, and hunting. Because logged tropical forests are extensive, functionally diverse, and provide many ecosystem services, efforts to expand their role in conservation strategies are urgently needed. Key priorities include improving harvest practices to reduce negative impacts on ecosystem functions and services, and preventing the rapid conversion and loss of logged forests.

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Maintaining ecosystem function and services in logged tropical forests

Woody biomass energy potential in 2050

Although increasing efforts are being made to restore tropical forests, little information is available regarding the time scales required for carbon and plant biodiversity to recover to the values associated with undisturbed forests. To address this knowledge gap, we carried out a meta-analysis comparing data from more than 600 secondary tropical forest sites with nearby undisturbed reference forests. Above-ground biomass approached equivalence to reference values within 80 years since last disturbance, whereas below-ground biomass took longer to recover. Soil carbon content showed little relationship with time since disturbance. Tree species richness recovered after about 50 years. By contrast, epiphyte richness did not reach equivalence to undisturbed forests. The proportion of undisturbed forest trees and epiphyte species found in secondary forests was low and changed little over time. Our results indicate that carbon pools and biodiversity show different recovery rates under passive, secondary succession and that colonization by undisturbed forest plant species is slow. Initiatives such as the Convention on Biological Diversity and REDD+ should therefore encourage active management to help to achieve their aims of restoring both carbon and biodiversity in tropical forests.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2013.2236

Carbon pools recover more quickly than plant biodiversity in tropical secondary forests

Tropical forest ecosystems are threatened by habitat conversion and other anthropogenic actions. Timber production forests can augment the conservation value of primary forest reserves, but studies of logging effects often yield contradictory findings and thus inhibit efforts to develop clear conservation strategies. We hypothesized that much of this variability reflects a common methodological flaw, simple pseudoreplication, that confounds logging effects with preexisting spatial variation. We reviewed recent studies of the effects of logging on biodiversity in tropical forests (n = 77) and found that 68% were definitively pseudoreplicated while only 7% were definitively free of pseudoreplication. The remaining proportion could not be clearly categorized. In addition, we collected compositional data on 7 taxa in 24 primary forest research plots and systematically analyzed subsets of these plots to calculate the probability that a pseudoreplicated comparison would incorrectly identify a treatment effect. Rates of false inference (i.e., the spurious detection of a treatment effect) were g0.5 for 2 taxa, 0.3n0.5 for 2 taxa, and l0.3 for 3 taxa. Our findings demonstrate that tropical conservation strategies are being informed by a body of literature that is rife with unwarranted inferences. Addressing pseudoreplication is essential for accurately assessing biodiversity in logged forests, identifying the relative merits of specific management practices and landscape configurations, and effectively balancing conservation with timber production in tropical forests.

Ahmad Dzamir Dzulkiply

Papers

Pseudoreplication in Tropical Forests and the Resulting Effects on Biodiversity Conservation