- ➔ Large areas of degraded land would benefit from restoration involving trees. Of the 2.2 billion ha of degraded land identified as potentially available for restoration worldwide, 1.5 billion ha may be best suited for mosaic restoration combining forests and trees with agriculture.
- ➔ Restoration involving trees can provide large environmental and economic benefits. For example, restoring degraded land through afforestation and reforestation could cost-effectively take 0.9–1.5 GtCO2e per year out of the atmosphere between 2020 and 2050. The restoration of 4 million ha of degraded land in the Sahara and the Sahel area has created more than 335 000 jobs.
- ➔ The scaling up of restoration and agroforestry is hindered by the time required to obtain profitable returns. For example, agroforestry can increase crop productivity in many local contexts, but obtaining a profitable return can take up to eight years compared with 1–2 years for annual crops.
The United Nations has declared 2021–2030 the Decade on Ecosystem Restoration, with the aims of preventing, halting and reversing ecosystem degradation on every continent and in every ocean; building political momentum; and creating a global movement and scaling up successful restoration actions. “Avoid degradation”, “reduce degradation” and “restore degraded land” are the three aspects of the response hierarchy in the forest and landscape restoration (FLR) approach.204 Restoration can pay its way, but it is usually cheaper to maintain ecosystems than to let them degrade and then undertake restoration.205 This section examines tree-based strategies for restoring degraded land, increasing agricultural productivity and maintaining or restoring ecosystem services with a view to increasing the resilience of both ecosystems and people.
In diverse contexts, the cost of restoration is much lower – up to 26 times – than the cost of inaction, and the environmental benefits can be considerable
An assessment in 42 African countries showed that the benefit of land restoration and conservation for agricultural productivity is 3–26 times greater than the cost of inaction.206 Mirzabaev et al. (2021) demonstrated that, in scenarios developed for Great Green Wall (GGW) countries, the costs of land restoration (cost of action) are lower than the costs of inaction, thus providing a strong economic justification for land restoration activities in the Sahel.207
Restoring degraded ecosystems can both enhance the provision of ecosystem services such as biodiversity conservation and water and climate regulation and spur economic growth – now, and beyond the pandemic.208 A meta-analysis of 89 studies in a broad range of ecosystem types worldwide, including forests, found that restoration increased the provision of biodiversity and ecosystem services by an average of 44 percent and 25 percent, respectively, relative to levels in degraded systems (measures of biodiversity were related to the abundance, species richness, diversity, growth and biomass of organisms present).209
Restoration can enhance key ecosystem services like water regulation and quality. Burek et al. (2016) estimated that 4.8 billion–5.7 billion people could be living in water-scarce areas at least one month per year by 2050.210 Investing in healthy forests would help in sustaining water services, with FLR a cost-effective measure for maintaining water-holding capacity, soil fertility and soil stability.211
The potential effects of restoration at the global level can be huge. Van der Esch et al. (2021) estimated that, between 2015 and 2050, without land restoration measures (baseline scenario), soil and biomass productivity will be negatively affected on 12 percent of the global land area; croplands will expand by about 20 percent (approximately 300 million ha) at the expense of natural areas; 6 percent of remaining biodiversity will be lost due to land-use change, intensive production and climate change; and average annual carbon emissions from land-use change and management over the period will amount to 16 percent of current annual emissions.212 A scenario in which restoration and protection measures are implemented to maintain ecosystem functions would result in 400 million ha more natural land compared with the baseline scenario, one-third of the projected global biodiversity loss would be prevented, and an additional 83 Gt of carbon would be stored in soils and vegetation, equivalent to more than seven years of current global emissions. On the other hand, limitations on land availability for agriculture would lead to increases in food prices.235
To be successful, restoration programmes require accurate and systematic designing, planning and monitoring and a combination of multiple balanced actions on the ground. Trees can play a significant role, but simply planting trees on degraded lands (especially in monocultures) is insufficient and a misconception of forest restoration. FLR goes beyond simply establishing forest cover, involving the restoration of whole landscapes to meet present and future needs and offering multiple benefits and land uses over time.213
Peatlands. GHG emissions from peatlands – such as after they are drained, or when they burn – are estimated to constitute about 5 percent of the global CO2 emissions caused by human activities.214 Dry, hot and windy weather conditions, which are already a reality in many regions,215 are leading to long-lasting peatland fires, even along the Arctic Circle.216 Declining rainfall, the thawing of permafrost and reduced glacier discharge combined with other complex phenomena that increase peat exposure to oxygen are threatening to turn an increasing area of peatland from GHG sinks to sources.
Smouldering peatland fires draw attention, but the draining of peatlands for cropping, grazing, forestry, energy and other uses is a long-term challenge. Drained peatlands continue to emit GHGs (and ecosystem services continue to decline) until they are rewetted. With peatland mapping and assessment advancing, an increasing number of countries are becoming aware of their depleting peatlands – and their ongoing emissions. Protecting peatlands from drainage, and restoring peatlands, have become priorities for many of the estimated 180 countries with peatlands,217 and knowledge and experience in peatland restoration have been accumulating since at least the 1970s.218 Improving peatland management is needed not only to safeguard carbon and reduce fire risk but also to protect coastal and riverine areas from subsidence, ensure flood protection and maintain water filtration services and biodiversity. The cost of peatland restoration is likely to be considerably lower than the estimated local and regional economic benefits, particularly in terms of human health due to reduced haze.219
Fire contributes more than 5 percent of greenhouse-gas emissions from agriculture, forestry and other land use. Integrated fire management is much less costly than firefighting
Biomass fires make a significant contribution to GHG emissions, representing more than 5 percent of total emissions from agriculture, forestry and other land use (according to recent unpublished FAO estimates). New estimates using FAOSTAT data indicate that GHG emissions due to biomass fire are roughly 30 percent higher than previously thought.220 The amount of money spent each year globally on fire management has been increasing, with the bulk in fire suppression: in the United States of America, for example, firefighting expenditure by federal agencies has increased from about USD 240 million in 1985 to USD 2.27 billion in 2020, a nearly tenfold increase.221 In Canada, the annual national cost of wildland fire protection (i.e. real increases in suppression costs and not the fixed costs to maintain firefighting personnel and programme management) have risen by about CAD 150 million per decade since data collection started in 1970.222 Few countries have assessed the overall economic burden of wildfire. An exception is the United States of America, where the annualized economic burden (all costs and impacts) of wildfire has been estimated at USD 71.1 billion to USD 348 billion (2016 dollars).223
Integrated fire management is widely accepted as an appropriate approach for ensuring that all aspects are considered in fire management planning and decision-making and can help reduce the overall cost burden of fire, especially by reducing the need for wildfire suppression and restoration.224 A recent study in the European Alpine region estimated the total direct cost of firefighting and post-fire management (excluding prevention measures) at around EUR 75 million per year; conversely, integrated fire management measures including prevention and suppression would cost around EUR 10 million per year. Ecosystem restoration is an important component of integrated fire management and can support the mitigation and prevention of future wildfires.
Restoration can generate substantial economic benefits, potentially yielding USD 7–30 for every USD 1 invested; the restoration of 4 million ha of degraded land in the Sahara and the Sahel created more than 335 000 jobs
Implementing restoration implies investment. For example, the investment required to achieve the Bonn Challenge (the restoration of 350 million ha by 2030) is estimated at more than USD 36 billion annually; the estimated cost of achieving land degradation neutrality globally is USD 318 billion per year between 2015 and 2030.225
Despite the attention that restoration is receiving globally, of the USD 14.6 trillion announced by the world’s 50 largest economies in fiscal spending as part of the COVID-19 recovery policies and stimulus plans, only about 2.5 percent is for green initiatives (which include nature-based solutions and green research and development).226 Only 3 percent of overall recovery spending is considered positive for natural capital and up to 17 percent could affect it negatively.227 This is a missed opportunity: restoration can provide some of the highest returns in the form of climate and environmental benefits, jobs and economic growth228 while also increasing land productivity. For example, it has been estimated that achieving the Bonn Challenge could take an additional 13–26 Gt of GHGs out of the atmosphere,229 delivering a net benefit of USD 0.7–9 trillion and USD 7–30 for every USD 1 invested.230 Roe et al. (2021) estimated that the restoration of degraded land through afforestation and reforestation could cost-effectively take 0.9–1.5 GtCO2e per year out of the atmosphere between 2020 and 2050 (see Table 4).231
Investments in FLR can generate considerable employment. For example, FLR actions created 354 000 short- and long-term jobs in five countries – Brazil, El Salvador, Mexico, Rwanda and the United States of America – as of 2018;232 these five countries have collectively committed to restoring 30.7 million ha of degraded land by 2030, mostly through forest-related activities (Figure 9).233
Figure 9The relative proportions of different restoration intervention types in Brazil, El Salvador, Mexico (Quintana Roo state), Rwanda and the United States of America, as of 2018
Dryland degradation has been valued at USD 6.3 trillion to USD 10.6 trillion per year, and 50 million people could be displaced because of it in the next ten years.234 Eleven sub-Saharan GGW member countries (Burkina Faso, Chad, Djibouti, Eritrea, Ethiopia, Mali, Mauritania, the Niger, Nigeria, Senegal and Sudan) have conducted land restoration and sustainable land management activities in the Sahara and the Sahel with the aim of increasing adaptation, mitigation and resilience to climate change, combating desertification, conserving biodiversity and ensuring sustainable development. When accounting for measures strictly within GGW intervention zones, 4 million ha of degraded land has been restored under the programme, generating approximately USD 90 million in revenue for rural people between 2007 and 2020 and creating more than 335 000 jobs, mainly in the implementation of restoration activities and the production and sale of NWFPs.235
Only a few long-term examples of successful FLR are available on how to implement the concept’s broadly accepted principles236 in practice. Moreover, there is a lack of systemization of information on FLR costs and benefits.237,238,239 A literature review of forest restoration costs in tropical and subtropical countries across a range of restoration interventions retrieved 61 relevant studies that provided restoration cost estimates in specific countries.240 Of these, 23 contained sufficiently robust data to allow the calculation of costs per unit area per year (Table 5). A collaborative international effort, The Economics of Ecosystem Restoration, is underway to obtain more data for economic analyses of landscape restoration to help in prioritizing investment in this process.241
Table 5Cost data retrieved from the literature on forest restoration in tropical and subtropical countries (23 studies)
In the absence of robust systematized cost–benefit data, restoring degraded ecosystems may be perceived as a costly or not-cost-efficient approach242 instead of an investment that can generate tangible returns in the future (as well as increase land productivity). Moreover, restoration comprises a wide suite of potential interventions, the upfront costs of which can vary enormously; “active” restoration can cost up to ten times more than natural regeneration approaches243 but may be needed where there is low site resilience;244 Box 10 presents an example in which an assisted natural regeneration approach cost about half as much as a more active approach such as tree-planting. The best restoration approach in a given situation depends on various economic, social and environmental factors. Underestimating the benefits and costs of restoration can increase the perceived investment risk. This is especially true in highly degraded landscapes, where the costs are usually considered too high and the direct economic benefits insufficiently tangible to attract investment.
Box 10Using assisted natural regeneration to restore a watershed in the Philippines
An assisted natural regeneration (ANR) project in the Danao municipality of Bohol, the Philippines, was implemented with the aim of restoring a highly degraded and deforested watershed area. Initially, considerable effort was required to encourage local stakeholders and authorities to change from conventional tree-planting approaches, although, at USD 579 per ha, the cost of ANR was almost half that of a conventional tree-planting approach in the area (USD 1 048 per ha). The cost is in line with indicative costs for ANR elsewhere in the tropics, at an average of USD 257 for direct establishment costs per ha in year 1 and annual maintenance and monitoring costs for the subsequent five years of up to USD 213 per ha. In Bohol, ANR interventions included establishing firebreaks, employing community members to conduct fire patrols, staking and protecting naturally regenerated seedlings and saplings, reducing competition from grasses by weeding and pressing, and controlling grazing and woodfuel-gathering. Farmers planted food crops in firebreaks to provide financial benefits during restoration. Observable changes in biodiversity were evident in grassland areas within 18 months, and tourism prospects also increased.
An analysis of 225 case studies in respect to benefits and 94 case studies in respect to costs showed that, even under a worst-case financial scenario, investing in restoration would return a financial profit in six of the nine ecosystem types assessed (Figure 10).245 Under a best-case scenario, restoration would generate positive benefit–cost ratios in all the ecosystem types considered. According to the analysis, tropical forest ecosystems offer among the best value for restoration investment in absolute terms (i.e. based on net present values and at social discount rates of 2 percent and 8 percent). Nevertheless, more data are needed to fully assess the costs and benefits of FLR policies and action and to enable cost-effectiveness and cost–benefit analyses and thereby help unlock and adequately allocate investment;246 increasingly, tools exist to help in maximizing the cost-effectiveness of FLR interventions (Box 11).
Figure 10Internal rates of return (a) and BENEFIT–COST ratio (b) for restoration in nine major biomes
Box 11Spatial planning optimization for the cost-effectiveness of forest and landscape restoration
Increasingly, spatial planning tools are available to maximize the benefits of restoration interventions and minimize the negative impacts of land-use decisions. The Restoration Opportunities Assessment Methodology,247 developed by the International Union for Conservation of Nature and the World Resources Institute, is a flexible cost-effective framework that can be used to identify priority areas and restoration interventions at the national and subnational levels. The WePlan-Forests platform,248 created by the International Institute for Sustainability and the Secretariat of the Convention on Biological Diversity, helps countries identify where forest and landscape restoration can achieve the greatest biodiversity and climate benefits; quantify trade-offs among multiple objectives of restoration; and fully harness the potential of natural regeneration as a cost-effective restoration strategy. A study on the use of WePlan-Forests in six pilot countries integrated spatially explicit estimates of where natural regeneration is possible with a model of establishment and opportunity costs to create new estimates of forest restoration costs; it demonstrated that accounting for natural regeneration in addition to active regeneration could reduce the establishment costs of forest restoration by 51–65 percent and create billions of US dollars in savings.249
Agroforestry increases biodiversity and carbon in landscapes and can increase smallholder income and resilience but requires incentives to cover risks and upfront costs
Agroforestry is a land-use system that involves the use of perennial woody species with agricultural crops or livestock in a given space and over a given period. Forty-three percent of all agricultural land globally – more than 1 billion ha – has at least 10 percent tree cover.250 The components of agroforestry (animals, crops and trees) can be combined in a wide range of production processes. The three main types of agroforestry system are: (1) agrosilvicultural (trees combined with crops); (2) silvopastoral (trees combined with animals); and (3) agrosilvopastoral (trees, animals and crops).
As an integrated agrifood system, agroforestry has the potential to advance global food security by increasing crop yield and resilience, providing ecosystem services, addressing land degradation and improving livelihood resilience.251 Of the 2.2 billion ha of degraded land identified as potentially available for restoration worldwide, 1.5 billion ha is considered best-suited for mosaic restoration in which forests and trees are combined with other land uses such as agroforestry, smallholder agriculture and settlements.252 The strategic establishment of trees on degraded land can increase agricultural productivity and the provision of ecosystem services, such as improved soil nutrient- and water-holding capacity and pest and weed management.253,254
It is estimated that agroforestry systems can contain 50–80 percent of the diversity of natural forests and can have 60 percent higher mean taxa richness than forests (consisting of both forest and non-forest species).255 This higher biodiversity includes above- and below-ground flora and fauna species, many of which (such as pollinators, soil organisms and mycorrhizae) can increase agricultural productivity. A global meta-analysis found that restored agroecosystems, such as agroforestry systems, increase overall species diversity by an average of 68 percent and the supply of ecosystem services by 42 percent.256 This is particularly significant for soil health, as noted in another recent meta-analysis, which found that agroforestry contributes to boosting ecosystem services, leading to a 50 percent reduction in soil erosion rates, a 21 percent increase in soil carbon storage, and a 46 percent increase in soil nitrogen availability to crops.257
The measurement of tree cover on agricultural land can be used to estimate the extent of agroforestry and assess the benefits of agroforestry systems, particularly in terms of carbon sequestration. In a global analysis, remote sensing data estimated that tree cover contributed at least 75 percent of the 45.3 GtC on agricultural lands in 2010.258 Tree cover on agricultural land increased by 3.7 percent between 2000 and 2010, which increased carbon storage by more than 2 GtC.259
Given the potential of agroforestry to help mitigate and adapt to climate change, 40 percent of non-Annex I countries under the UNFCCC propose this land use as a solution in their NDCs, with the measure embraced most widely in Africa (contained in 71 percent of NDCs), followed by the Americas (34 percent of NDCs), Asia (21 percent) and Oceania (7 percent); 50 percent of the 73 developing countries with REDD+ strategies have identified agroforestry as a way to combat forest decline.260 The COVID-19 pandemic has further highlighted the importance of diversified, resilient, localized production systems for maintaining animal, human and ecological health.
The land-equivalent ratio, defined as the ratio of the area under sole cropping to the area under intercropping needed to give equal amounts of yield at the same management level, is commonly used for comparing productivity in terms of biomass and other yields. In a study of five agroforestry systems in five European countries, the adoption of agroforestry was shown to increase agronomic productivity by 36–100 percent (i.e. a land-equivalent ratio of 1.36–2.00), depending on crop type, crop arrangement and management, and local conditions.261 Kuyah (2019) analysed 126 peer-reviewed studies on agroforestry in sub-Saharan Africa and concluded that, on average, agroforestry systems increased crop yield while maintaining the delivery of regulating/maintenance ecosystem services.262
Agroforestry is a potential option for maintaining ecological balance and diversifying rural livelihoods (Box 12).263 To date, however, it has been promoted primarily for subsistence, and many of its benefits have not been adequately quantified. The distributional ranges of both costs and benefits are highly variable, even within individual practices and systems.
Box 12An agroforestry model in the Brazilian Amazon
Farmers in Tomé-Açu in the eastern Amazon in Brazil have developed a farmer-led agroforestry model known as SAFTA, which combines market-oriented agroforestry systems and local agro-industry, adding value to agroforestry products and promoting exports to national and global markets. SAFTA is a transitional agroforestry system that involves short-term annual crops, medium-term perennial crops and long-term fruit and timber tree species.274 In the past, SAFTA has been supported by the federal and state governments, and currently it is supported by local governments (and it has been branded as a means to position its products in local and international markets).275 Although SAFTA can take various forms, it is usually based on a combination of 1–3 valuable cash crops (e.g. cocoa, cupuaçu, black pepper and açai) and the production of oils, resins and timber.276
Agroforestry is a longer-term investment than conventional agriculture, requiring longer profit forecasts and planning;264,265 it can also incur high establishment and maintenance costs, sometimes generating net losses in the first few years.266 On average, agroforestry sees profitable returns after 3–8 years; for annual cropping systems, this period is normally 1–2 years.
Agroforestry systems are more resilient than conventional agricultural systems to environmental shocks and the effects of climate change, such as severe storms, droughts and floods, due largely to the diversity of benefits they provide.267 They increase food security and nutrition by serving as safety nets during such shocks,268 especially when these affect entire communities rather than single households.269 In an upland area of the Philippines, for example, smallholder farmers who adopted agroforestry had 42–137 percent higher earning capacity and food security than farmers who practised annual monocropping.270
Despite the wide-ranging environmental benefits of agroforestry, its adoption and scaling up face challenges, many of which are socio-economic in nature, including labour, gender and farm size.271 High establishment costs and longer-term returns, access to capital and markets, knowledge and capacity management, and land-tenure insecurity all represent significant barriers to the uptake of agroforestry by farmers. Smallholder producers face trade-offs between alternative land uses, such as monocropping, and need to assess the comparative profitability of a given practice, including whether the practice is culturally appropriate.272 Although numerous studies have demonstrated the higher productivity of agroforestry systems, many farmers perceive such systems as less productive and thus financially unviable or risky.273
The greater uptake of agroforestry requires effective incentives and strategic investments to achieve restoration and improved production objectives, such as providing support for tree establishment, increasing the knowledge and capacity of smallholders and extension professionals in tree-growing, and improving access to markets.277,278,279
Government incentives, redesigned agricultural credits and payments for ecosystem services can help address the significant barrier of limited short-term cashflow. In Peru, a national policy on agroforestry concessions grants land rights to smallholders who encroached forest land before 2011 on the condition that they conserve and sustainably manage forests and establish agroforestry.280 Given adequate carbon prices and institutional support, payments for carbon sequestration may further incentivize uptake.304 A study in Ethiopia found that carbon revenue made agroforestry more profitable than monocropping, with carbon revenue being even higher than the net revenue of any monoculture plot when the sequestration rate was high and the price of carbon was at its highest.281
Green recovery from the pandemic is an opportunity to increase the restoration effort and thereby create jobs and enable long-term increases in land productivity
As of 2020, nearly two-thirds of the USD 115 billion per year in public funds invested in nature-based solutions is being spent on restoration (forest and peatland restoration, regenerative agriculture, water conservation and natural pollution control systems).282
Building back after the COVID-19 pandemic requires not only economic growth but also supporting productive healthy ecosystems (i.e. “green” recovery). Given their potentially high economic returns,283 the forest sector and nature-based approaches like FLR, peatland rewetting and agroforestry can be effective as part of a green recovery. The potential environmental and socio-economic benefits of FLR and agroforestry are immense, but so too are the challenges of planning and implementing successful interventions on the ground. Thus, considerable effort is needed to compile and share data and knowledge on FLR and agroforestry and how to put these into effect efficiently and to optimize the benefits.