Direct and indirect drivers of land degradation and restoration

Abstract

Human activities now represent the most important force shaping the degradation of ecosystems in all of the world´s major biomes (well established). Long-established drivers of land degradation continue to increase across much of the world, including agricultural activities {3.3.1, 3.3.2}, driven by increasing demands for food and bioenergy. More recent global change drivers, such as climate change and atmospheric nitrogen deposition, further exacerbate impacts {3.4}. We are now in a qualitatively different and novel world, compared to only a few decades ago, and the combination of drivers creates significant challenges to restore degraded land and mitigate further degradation (established but incomplete). Few, if any, areas of the world are now free of some form of human influence (well established) and some systems are experiencing unprecedented challenges. Changes in the extent and severity of both land degradation and restoration commonly result from multiple underlying social and economic factors – indirect drivers, many of which occur in places distant from where the impacts are felt (well established) {3.6.4}. Demand for food imports is increasing across much of the world. This high dependency on imported commodities means that a large share of the environmental impacts of consumption is felt in other parts of the world. The physical quantity of goods traded internationally only represents one third of the actual natural resources that were used to produce these traded goods. The sustainability of the commodity production systems that support global supply chains is thus substantially shaped by the sourcing and investment decisions of market actors who may have little direct connection to the production landscapes (established but incomplete). Moreover, the globalized nature of many commodity supply chains potentially elevates the relative importance of global-scale factors such as trade agreements, market prices and exchange rates, as well as distant linkages related to buyer and investment preferences, over national and regional governance arrangements and the agency of individual producers (inconclusive). Addressing this complexity to avoid and reverse land degradation therefore requires the building of effective multi-sector and multi-stakeholder partnerships that span national boundaries (established but incomplete) {3.6.6}. Economic growth and per capita consumption, more than poverty, is one of the biggest threats to sustainable land management globally (established but incomplete) {3.6.3, 3.6.4}. Extreme poverty, combined with resource scarcity, can contribute to land degradation and unsustainable levels of natural resource use, but is rarely the major underlying cause (well established). Many of the most marked changes in how land is used and managed come from individual and societal responses to economic opportunities, such as a shift in demand for a particular commodity or improved market access, moderated by institutional and political factors (established but incomplete). For example, clearance of native vegetation and land degradation across much of Latin America and Asia is linked to agricultural expansion and intensification at a commercial scale for export markets (well established). Reducing poverty, although a priority for sustainable development, is insufficient to mitigate land degradation if not accompanied by additional measures. Concurrently, rising per capita consumption levels can exacerbate degradation. Efforts to reverse degradation therefore require a combination of local and regional poverty-alleviation strategies, including the adoption of pro-poor food production systems, together with efforts to improve the enforcement of public regulations for sustainable land uses, and strengthening the accountability of global market actors in effectively supporting such strategies. The highly interconnected and globalized nature of indirect drivers of land degradation and restoration means that the outcome of any global, regional or local intervention can be highly unpredictable, yet contextual generalizations are possible (established but incomplete) {3.6.2.3, 3.6.3}. The ways in which land is used in one part of the world can be highly sensitive to sudden, unexpected changes in economic and institutional factors elsewhere (unresolved). For example, changes in currency exchange rates, and cascading effects on the profitability of a given commodity, can markedly accelerate or decelerate the clearance of native vegetation for agriculture within a single year {3.6.2.3}. The sudden imposition of trade restrictions (e.g., due to disease controls), can have a similarly marked impact. However, with an improved understanding of the interactive effects amongst different drivers, it is possible to make predictions that are valid under a certain range of conditions. For example, agricultural intensification and agroforestry practices can help reduce the pressure on remaining areas of native vegetation under certain conditions (such as inelastic demand for staple crops), but unless such measures are coupled with increased enforcement of land-use policies they can result in a rebound effect that increases pressure on natural resources (established but incomplete) {3.6.3}. Land degradation in any given place is rarely the consequence of a single anthropogenic driver, but is instead the result of a diverse and frequently mutually-reinforcing set of human activities and underlying drivers (well established) {3.4.5, 3.5, 3.6.2.1}. Typically, at least three types of indirect driver, such as economic, technological and institutional, underpin any direct driver of land degradation or restoration (established but incomplete). The complexity of drivers that commonly underpin land degradation highlights the fact that single factors, such as high rural population density, rarely provide an adequate underlying explanation on their own for observed impacts (established but incomplete) {3.6.3}. Land degradation is typically the result of multiple direct drivers, especially in instances of severe degradation (e.g., where land-use intensification drives increased species invasions and increases in fire frequency). This combination of drivers has resulted in large expanses of economically important grazing lands, including in North America, being transformed to fire-prone annual grass monocultures (well established) {3.3.7}. The multi-causality of land degradation requires commensurately holistic policy responses that operate across multiple scales and combine both regulatory and incentive based measures (established but incomplete). Rapid expansion and inappropriate management of agricultural lands (including both grazing lands and croplands), especially in dryland ecosystems, is the most extensive land degradation driver globally (well established) {3.3.1, 3.3.2}. The expansion of grazing lands has largely stagnated globally with evidence for an approximate 1% decline in grazing land area over the past decade. Grazing pressure has been stable or only moderately increasing across the major land areas globally, although there are regional exceptions such as Southern Asia. Over half of grazing lands occur in dryland environments that are highly susceptible to land degradation (established but incomplete) {3.3.1.3}. More recently intensification and increasing industrialization of livestock production systems, especially in developed countries, has resulted in an increasing reliance on mixed crop-livestock production systems and industrialized "landless" systems. As a result, 35% of global crop production is now allocated to livestock feed. Globally, fertilizer and pesticide use is expected to double by 2050 {3.3.2.2}. Marked drops in nitrogen-use efficiency (change in yield per unit of fertilizer input) in many parts of the world, particularly the Asia Pacific region, often accompanied by continued excessive fertilizer application, underscore the critical importance of sustainable agricultural practices, including conservation agricultural techniques, to maintain yield improvements (established but incomplete) {3.3.2.3}. Increases in consumption levels of many natural resources underpin increasing levels of degradation in many parts of the world (well established), with slow rates of adoption of sustainable production systems (established but incomplete) {3.6.2.2, 3.6.3.2, 3.6.4.2}. Projections to 2050 suggest that one billion ha of natural ecosystems could be converted to agriculture by that time. More than half of agricultural expansion in the last three decades has occurred in relatively intact tropical forests. Economic growth in the developing world is projected to double global consumption of forest and wood products by 2030, with demand likely to exceed production in many developing and emerging economies in Asia and Africa within the next decade. Traditional fuelwood and charcoal continue to represent a dominant share of total wood consumption in low income countries, up to 70%, especially in Sub-Saharan Africa (well established). Under current projections efforts to intensify wood production in plantation forests, together with increases in fuel-use efficiency and electrification are only likely to partly offset the pressure on native forests (unresolved). Adoption of more sustainable production systems continues to be slow, as seen, for example, by a slowdown in the expansion of the area of certified forests. More than half of the terrestrial surface of the Earth has fire regimes outside the range of natural variability, with changes in fire frequency and intensity posing major challenges for land restoration (established but incomplete) {3.3.7}. The frequency of fires has increased in many areas – exacerbated by decreases in precipitation – including in many regions of humid and temperate forests that rarely experience large-scale fires naturally. Some changes in fire regimes, particularly in tropical forests, are sufficiently severe that recovery to pre-disturbance conditions may no longer be possible. Increases in international trade, intensification of land use and urbanization have meant that few areas of the planet are free of invasive species (established but incomplete) {3.3.8}. Nearly one fifth of the Earth´s surface is at high risk of plant and animal invasion, including many biodiversity hotspots. Climate change, including increased nitrogen deposition and changes in CO2, as well as increases in fire frequency with rising temperatures in many areas, are all likely to increase invasions {3.4}. Once established, the eradication of many invasive species is often very expensive, if not impossible, underscoring the need to develop proactive strategies to pre-empt invasions, including through inspections, research and education. Activities related to industrialization, infrastructure development, urbanization, and many extractive industries result in complete transformation of ecosystems, accompanied by near or complete loss of biodiversity and ecosystem function and the services those ecosystems provide (well established) {3.3.6}. Infrastructure, industrial development and urbanization activities, often replace natural ecosystems with impervious or contaminated surfaces such as asphalt, concrete and rooftops, leading to the one of the most severe forms of land degradation in the form of soil sealing. Built-up areas, which are dominated by sealed soils, currently occupy nearly 0.6% of the global land surface. If population densities in cities remain stable, the extent of built-up areas in developed countries is expected to increase by 30% and triple in developing countries between 2000 and 2050. Under more extreme scenarios of increasing population density and economic development, the extent of built-up areas globally may increase to over 2% of the global land area over this same time period. New urban design and green technologies that incorporate features that promote sustainability and delivery of ecosystem services can play an important role in restoring some of the ecosystem functions and services of built environments. The importance of climate change for land degradation is most prominent through its role in exacerbating the impacts of other human activities (established but incomplete) {3.4}. The exacerbating effect of climate change on the impact of degradation drivers, including land clearance and intensive farming techniques, can be felt both through chronic impacts and directional changes – like temperature changes, leading to shifts in species range sizes, as well as changes in average precipitation levels, atmospheric CO2 and nitrogen deposition – and acute impacts through extreme weather events of flooding, drought, and other natural disasters (well established). Heavy rainfall events and storms as well as heat waves and droughts are predicted to increase in frequency over several parts of the globe, with cascading effects on the frequency, intensity, extent and timing of other drivers such as fires, pest and pathogen outbreaks, species invasions, soil erosion and landslides (established but incomplete). The last decade has witnessed a rise in consumer-driven demand for sustainable land use and land management, as well as commitments to restore degraded land that is unprecedented in human history (well established) {3.6}. In the last decade hundreds of companies have made pledges to reduce their impacts on forests and on the rights of local communities, with many committing to eliminate deforestation from their supply chains entirely by 2020. In the same period, many governments and civil society groups have made ambitious commitments to restore hundreds of millions of hectares of degraded land. New players, such as the finance sector, who until recently have been completely detached from the mainstream sustainability agenda are also starting to make explicit commitments to avoiding environmental harm. The overall impact of these voluntary measures remains to be assessed but they offer a vital window of opportunity for reversing degradation trends and placing economies on a more sustainable footing – especially as large areas of marginal agricultural become increasingly abandoned with ongoing development (unresolved).