Quantifying how well Nature-based Solutions can offset anthropogenic climate change impacts is important for adaptation planning, but has rarely been done. Here we show that a widely-applied Nature-based Solution in South Africa – invasive alien tree clearing – reduces the impact of anthropogenic climate change on drought streamflow. Using a multi-model joint-attribution of climate and landscape-vegetation states during the 2015–2017 Cape Town “Day Zero” drought, we find that anthropogenic climate change reduced streamflow by 12–29% relative to a counterfactual world with anthropogenic emissions removed. This impact on streamflow was larger than corresponding reductions in rainfall (7–15%) and reference evapotranspiration (1.7–2%). Clearing invasive alien trees could have ameliorated streamflow reductions by 3–16% points for moderate invasions levels. Preventing further invasive alien tree spread avoided potential additional reductions of 10–27% points. Total clearing could not have offset the anthropogenic climate change impact completely. Invasive alien tree clearing is an important form of catchment restoration for managing changing hydroclimatic risk, but will need to be combined with other adaptation options as climate change accelerates.
Habitat Type: GR_MED
Mediterranean shrublands and woodlands
1. Abandonment of agricultural land is widespread in many parts of the world, leading to shrub and tree encroachment. The increase of flammable plant biomass, that is, fuel load, increases the risk and intensity of wildfires. Fuel reduction by herbivores is a promising management strategy to avoid fuel build-up and mitigate wildfires. However, their effectiveness in mitigating wildfire damage may depend on a range of factors, including herbivore type, population density and feeding patterns.
2. Here, we review the evidence on whether management with herbivores can reduce fuel load and mitigate wildfires, and if so, how to identify suitable management that can achieve fire mitigation objectives while providing other ecosystem services. We systematically reviewed studies that investigated links between herbivores, fire hazard, fire frequency and fire damage.
3. We found that, in general, herbivores reduce fuel load most effectively when they are mixed feeders, when grazing and browsing herbivores are combined and when herbivore food preferences match the local vegetation. In some cases, the combination of herbivory with other management strategies, such as mechanical clearing, is necessary to reduce wildfire damage.
4. Synthesis and Applications. We conclude that herbivores have the capacity to mitigate wildfire damage, and we provide guidance for grazing management for wildfire mitigation strategies. As areas undergoing land abandonment are particularly prone to wildfires, the maintenance or promotion of grazing by domestic or wild herbivores is a promising tool to reduce wildfire risk in a cost-effective way, while also providing other ecosystem services. Relevant land-use policies, including fire suppression policies, agricultural and forest(ry) policies could incentivise the use of herbivores for better wildfire prevention.
Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO2) emitted by human activities each year1, yet the persistence of this carbon sink depends partly on how plant biomass and soil organic carbon (SOC) stocks respond to future increases in atmospheric CO2 (refs. 2,3). Although plant biomass often increases in elevated CO2 (eCO2) experiments4,5,6, SOC has been observed to increase, remain unchanged or even decline7. The mechanisms that drive this variation across experiments remain poorly understood, creating uncertainty in climate projections8,9. Here we synthesized data from 108 eCO2 experiments and found that the effect of eCO2 on SOC stocks is best explained by a negative relationship with plant biomass: when plant biomass is strongly stimulated by eCO2, SOC storage declines; conversely, when biomass is weakly stimulated, SOC storage increases. This trade-off appears to be related to plant nutrient acquisition, in which plants increase their biomass by mining the soil for nutrients, which decreases SOC storage. We found that, overall, SOC stocks increase with eCO2 in grasslands (8 ± 2 per cent) but not in forests (0 ± 2 per cent), even though plant biomass in grasslands increase less (9 ± 3 per cent) than in forests (23 ± 2 per cent). Ecosystem models do not reproduce this trade-off, which implies that projections of SOC may need to be revised.
The climate and biodiversity crises are fundamentally connected and more integrated approaches are needed to address them effectively. To directly tackle the interconnected factors behind them, actions which
capitalize on the contributions of nature, commonly known as Naturebased Solutions (NbS), can play a more central role. The one-year delay in the 2020 Conferences of Parties to the UNFCCC and the CBD caused by the COVID-19 crisis provides a unique opportunity to bring new scientific advances to inform and strengthen the links between both international agendas and their national implementation. To facilitate the alignment and better understand the potential synergies between these agendas, there is a need to assess the role that achieving biodiversity conservation targets can play in efforts to mitigate climate change. This report presents the first results of ongoing research aiming to inform progress by making explicit and quantifying the role that achieving biodiversity conservation targets can play in securing the emissions reductions needed to meet the objectives of the Paris Agreement. This report, the first output of this effort, looks at the carbon stocks associated with areas identified as possible priorities to meet proposed global biodiversity conservation targets.
The analysis presented here identifies the regions where global action will deliver the most to achieve post-2020 biodiversity conservation goals and mitigate climate change. It shows that the strategic choice of areas to be managed for conservation, increasing such areas to 30% of land globally,
could safeguard more than 500 gigatons of carbon. When prioritizing
areas for conservation management, taking account of biodiversity and
carbon together can secure 95% of the biodiversity benefits and nearly
80% of the carbon stock that could be obtained by prioritizing based on
either value alone. [Continued]
Extensive ecosystem restoration is increasingly seen as being central to conserving biodiversity1 and stabilizing the climate of the Earth2. Although ambitious national and global targets have been set, global priority areas that account for spatial variation in benefits and costs have yet to be identified. Here we develop and apply a multicriteria optimization approach that identifies priority areas for restoration across all terrestrial biomes, and estimates their benefits and costs. We find that restoring 15% of converted lands in priority areas could avoid 60% of expected extinctions while sequestering 299 gigatonnes of CO2—30% of the total CO2 increase in the atmosphere since the Industrial Revolution. The inclusion of several biomes is key to achieving multiple benefits. Cost effectiveness can increase up to 13-fold when spatial allocation is optimized using our multicriteria approach, which highlights the importance of spatial planning. Our results confirm the vast potential contributions of restoration to addressing global challenges, while underscoring the necessity of pursuing these goals synergistically.
Nature-based solutions (NBS) are usually defined as complementary or alternative solutions to “grey infrastructures” (traditionally made with cement) aimed at conserving and regenerating the functionality of natural and semi-natural ecosystems. The research to date shows a considerable potential of NBS to address the current challenges related to climate change and geo-hydrological risks. Despite significant interest in NBS by researchers and practitioners, knowledge concerning their practical implementation, monitoring, and evaluation is still lacking. This is particularly true for large-scale NBS. The present paper discusses how such solutions can be implemented in the context of hydro-meteorological risk reduction in small Mediterranean catchments with a strong tourist vocation. The work presented here is situated within the RECONECT Project (Regenerating ECOsystems with Nature-based solutions for hydro-meteorological risk rEduCTion), which aims to contribute to a European reference framework on NBS by demonstrating, upscaling, and replicating large-scale NBS in rural and natural areas. The Italian case study of RECONECT is the Portofino Natural Regional Park, which represents a unique natural landscape element with high ecologic, social, and economic (touristic) value, which is threatened by a range of geo-hydrological hazards, such as flash floods, hyper-concentrated floods, shallow landslides, rockfalls, and storm surges. This paper also presents details of NBS interventions in two pilot catchments (San Fruttuoso and Paraggi) visited by thousands of tourists throughout the year. It addresses some of the key aspects related to monitoring meteorological and hydrological processes, as well as remote sensing activities (i.e., LiDAR surveys), which are necessary for the identification of critical-instability areas along waterways and the reconstruction of dry stone walls. Lastly, a discussion of relevant mitigation and adaptation strategies that are potentially replicable at national and international levels is also provided.
The concept and establishment of Ecological Networks (EN) have been seen as a solution towards nature conservation strategies targeting biodiversity and ecological connectivity. Within this, the EN assumed a holistic view of land-use planning and biodiversity conservation as the core of the wider Green Infrastructure (GI) framework. The EN is considered a spatial concept recognized as a system of landscape structures or ecosystems, and a strategically connected fundamental infrastructure of abiotic and biotic systems, underlying the provision of multiple functions valuable to society. This concept moves beyond traditional approaches of “nature protection and preservation”, (re)focusing on the ecosystemic approach and the “continuum naturale”, emphasising the quality or potentiality of physical components, allowing the articulation with the nature conservation and at-risk areas. Portugal has long had legislation in place meant to protect the natural resources. Although the environmental policies are sectoral and unarticulated, and the environmental data is dispersed and absent. In addition, this study shows that the existing protected areas in Portugal, namely Natura 2000 and classified protected areas, are insufficient to ensure landscape ecological balance and avoid fragmentation. The main goal is to develop a methodology to map a National Ecological Network (NEN) for mainland Portugal, establish the theoretical framework of the EN/GI, by identifying and mapping the most valuable and sensitive areas that guarantee the ecosystem functioning through a multi-level ecological evaluation criteria that integrate the physical and biological systems. The Portuguese NEN map, with a 25 m spatial resolution, integrates in a single tool the Portuguese environmental policies more effectively, in order to facilitate its understanding and application into planning. Regarding the EN mapping method, it was used a GIS-based model made up of a sequence of analyses and evaluations that are driven by a GIS supported assessment of several indices/models used for each EN component. These NEN components were studied individually and collectively and the results, hierarchized in two levels, show that most of the ecological components do not overlap. The NEN1 has high biodiversity and ecological value, which means they are more vulnerable to anthropogenic activity. NEN1 covers a total of 67 % of the mainland, yet as of 2018, only 25 % is protected in nature conservation areas. Priority of action must be given to NEN1 in order to avoid/decrease landscape fragmentation, environmental risks, and natural disaster prevention. This paper contributes to the understanding of the NEN importance as an ecologically based tool towards a more sustainable landscape planning, and the basis of the development plans at national, regional and local levels in an integrated manner, instead of a compilation of disassociated often-contradictory planning tools. The benefits of a Portuguese NEN into a GI development and part of a (broader) nature base solutions by increasing the ecosystems quality and become less dependent on economic and social activities, helping in the restoration of degraded ecosystems and environmental risk prevention. Moreover, it represents the first attempt to map Portuguese EN, and addresses the lack of mapping and the inconsistent EN criteria. It is available online at http://epic-webgis-portugal.isa.ulisboa.pt.
Limiting climate warming to <2°C requires increased mitigation efforts, including land stewardship, whose potential in the United States is poorly understood. We quantified the potential of natural climate solutions (NCS)—21 conservation, restoration, and improved land management interventions on natural and agricultural lands—to increase carbon storage and avoid greenhouse gas emissions in the United States. We found a maximum potential of 1.2 (0.9 to 1.6) Pg CO2e year−1, the equivalent of 21% of current net annual emissions of the United States. At current carbon market prices (USD 10 per Mg CO2e), 299 Tg CO2e year−1 could be achieved. NCS would also provide air and water filtration, flood control, soil health, wildlife habitat, and climate resilience benefits.
The Mediterranean evergreen oak coppices of Southern Europe are increasingly vulnerable to drought because of both the ongoing climate change that increases drought length and intensity, and the lack of forest management that induces a structural aging of the stands. Decreasing stand density through thinning has been widely regarded as a means to improve the resistance of evergreen oak forests to climate change by decreasing the competition for water amongst the remaining stems. Data from a 30-years thinning experiment, that includes a control and four thinning intensity treatments (from 25% to 80% of basal area removed), in a coppiced holm oak (Quercus ilex L.) forest of southern France, was used to quantify the effects of thinning on stem growth. Building on the ‘sink limitation’ paradigm, which proposes that tree growth is controlled by phenology and climatic constraints and decoupled from carbon assimilation, we investigated if the effect of thinning on stem growth was explained by a delayed drought-induced growth cessation. Using a water balance model, we simulated the date of drought-induced growth cessation, previously found to correspond to the day of the year when water potential drops below a threshold of -1.1 MPa, and used it to predict growth in the different treatments of the thinning experiment. Thinning increased long-term growth at the stem level but decreased the wood biomass at the stand level. Decreasing stem density, and hence the leaf area index, was simulated to delay the date of drought-induced growth cessation. A growth model based on the date of growth cessation explained 85% of the effect of thinning on stem growth over the 30-year period of the study, and 95% for the first five years after thinning. The canopy density for which the effect of thinning is the most beneficial was found to maximize the growth duration without lifting completely the water limitation in summer. Moderate thinning had a sustained beneficial effect on the growth of all stem size classes, whereas stronger thinning intensities increased the size asymmetry of competition and their overall effect dropped faster. Our simple predictive model based on the simulation of the water balance as a function of stand density opens the way to providing management guidelines for the optimization of tree density as a function of water limitation in Mediterranean evergreen woodlands.
Planted and invading non-native plant species can alter fire regimes through changes in fuel loads and in the structure and continuity of fuels, potentially modifying the flammability of native plant communities. Such changes are not easily predicted and deserve system-specific studies. In several regions of the southern hemisphere, exotic pines have been extensively planted in native treeless areas for forestry purposes and have subsequently invaded the native environments. However, studies evaluating alterations in flammability caused by pines in Patagonia are scarce. In the forest-steppe ecotone of northwestern Patagonia, we evaluated fine fuels structure and simulated fire behavior in the native shrubby steppe, pine plantations, pine invasions, and mechanically removed invasions to establish the relative ecological vulnerability of these forestry and invasion scenarios to fire. We found that pine plantations and their subsequent invasion in the Patagonian shrubby steppe produced sharp changes in fine fuel amount and its vertical and horizontal continuity. These changes in fuel properties have the potential to affect fire behavior, increasing fire intensity by almost 30 times. Pruning of basal branches in plantations may substantially reduce fire hazard by lowering the probability of fire crowning, and mechanical removal of invasion seems effective in restoring original fuel structure in the native community. The current expansion of pine plantations and subsequent invasions acting synergistically with climate warming and increased human ignitions warrant a highly vulnerable landscape in the near future for northwestern Patagonia if no management actions are undertaken.
The Mediterranean Mosaics Project has the objective to increase the resilience of forest ecosystems in the Shouf Biosphere Reserve (SBR) to climate change. The Project has designed adaptive forest restoration and management plans that were applied in a number of pilot sites over the 3 years of Project implementation: (i) sustainable forest thinning and pruning operations were applied in 18.5 ha of Quercus calliprinos and Pinus brutia forestland; (ii) ecological restoration techniques were tested and demonstrated in 59.11 ha. Seeds and seedlings of about 38 plant species were used, with the objective to restore the forest habitats and ecological processes by which the species populations can self-organize into functional and resilient communities well-adapted to changing climate conditions, while at the same time delivering vital ecosystem services. Ad-hoc plant production protocols were developed to ensure the production of high-quality and well-hardened seedlings. The project has demonstrated the possibility to implement forest restoration without additional water supply to the planted seedlings. The survival rate in the majority of sites after 3 years was between 75% and 100%, with the exception of the direct seed sowing of oak acorns (up to 20%) that were very much affected by rodent predation. Only in instable soil debris direct seed sowing of Quercus acorns has achieved a very high survival rate up to 100%. The key factors of success in the Project forest restoration work were: (i) the availability of high quality plant material from the selected species; (ii) a good preparation of the soil and careful planting of seedlings to facilitate the growth of the root system, and increase soil water retention and storage; (iii) the selection of the right planting period, making sure that soil is sufficiently wet. The Project has also demonstrated the environmental and socio-economic benefits of the combined use of forest thinning and pruning products and agriculture waste (olive pomace and waste wood from fruit tree pruning). Lessons learned from the pilot demonstration actions have opened up new opportunities to influence forestation plans in the Country, and regulate the harvesting of forest biomass and its combined use with agricultural waste to control the risk of forest fires, generate economic benefit and contribute to local livelihoods.
We analysed the extent of ecological damage of gully and inter‐gully erosion in a sub‐catchment situated in the drylands (300 mm yr−1) of the winter rainfall area of South Africa where small‐stock farming on rangeland is the main source of income. We applied low‐cost measures to revegetate the bare sites of the inter‐gully erosion and stabilised gully erosion by loosening soil surfaces and applying geotextile and constructing check dams to reverse gully erosion. We compared vegetation cover, silt accumulation and penetration resistance of the soil upslope of the check dams with the situation downslope of the check dams and untreated gullies as controls. For the treated bare patches, we compared penetration resistance and vegetation cover with untreated controls. Two years after implementation, the restoration measures resulted in increased soil depth and vegetation cover upslope of the check dams and increased vegetation cover on the treated bare patches. We calculated the net present value of the restoration measures based on the financial benefit that a landowner can realistically expect under current economic and governance conditions (i.e. payment for additional livestock and for C sequestration). At the current rates of return for livestock production or carbon sequestration over a 20‐year period, rehabilitation of this sort is not financially feasible for private landowners. Either the current payment for carbon sequestration would have to be increased by a magnitude of 40–80, or restoration measures would have to be funded by the public or private sector to make them financially viable for landowners.
Forests are sources of wood, non-timber forest products and ecosystems services and goods that benefit society as a whole, and are especially important to rural livelihoods. Forest landscape restoration (forest-landscape-restoration:Forest landscape restoration) has been proposed as a way to counteract deforestation and reconcile the production of ecosystem services and goods with conservation and development goals. But limited evidence indicates how large-scale forest restoration could contribute to improving local livelihoods. Here, we present a conceptual framework to analyze the effects of large-scale restoration on local livelihoods, and use it to review the scientific literature and reduce this knowledge gap. Most of the literature referred to case studies (89%), largely concentrated in China (49%). The main theme explored was income, followed by livelihoods diversification, off-farm employment opportunities, poverty reduction, equity and the provision of timber and energy as ecosystem services. Nearly 60 percent of the papers discussed the importance of governance systems to socioeconomic outcomes. The reforestation/restoration programs and policies investigated in the studies had mixed socioeconomic effects on local livelihoods depending on other variables, such as availability of off-farm jobs, household characteristics, land productivity, land tenure, and markets for forest products and ecosystem services. We conclude that the effects of large-scale restoration initiatives on local livelihoods may vary due to several factors and is still not clear for many situations; therefore, monitoring over time with clear indicators is needed.
Many US forest managers have used historical ecology information to assist in the development of desired conditions. While there are many important lessons to learn from the past, we believe that we cannot rely on past forest conditions to provide us with blueprints for future management. To respond to this uncertainty, managers will be challenged to integrate adaptation strategies into plans in response to changing climates. Adaptive strategies include resistance options, resilience options, response options, and realignment options. Our objectives are to present ideas that could be useful in developing plans under changing climates that could be applicable to forests with Mediterranean climates. We believe that managing for species persistence at the broad ecoregion scale is the most appropriate goal when considering the effects of changing climates. Such a goal relaxes expectations that current species ranges will remain constant, or that population abundances, distribution, species compositions and dominances should remain stable. Allowing fundamental ecosystem processes to operate within forested landscapes will be critical. Management and political institutions will have to acknowledge and embrace uncertainty in the future since we are moving into a time period with few analogs and inevitably, there will be surprises.
In the 1980s, Professor Akira Miyawaki introduced a new and innovative reforestation approach in Japan with the challenge to restore indigenous ecosystems, and maintaining global environments, including disaster prevention and carbon dioxide (CO2) mitigation. Here, natural vegetation successional stages (from bare soil to mature forest) are practically forced and reproduced, accelerating natural successional times. The Miyawaki method has been applied in the Far East, Malaysia, and South America; results have been very impressive, allowing quick environmental restorations of strongly degraded areas. However, these applications have always been made on sites characterized by high precipitation. The same method has never been used in a Mediterranean context distinguished by summer aridity and risk of desertification. A first test was carried out by the University of Tuscia, Department of Forest and Environment (DAF), 11 years ago in Sardinia (Italy) on an area where traditional reforestation methods had failed. For an appropriate Miyawaki application on this site, the original method was modified while maintaining its theoretical principles. Results obtained 2 and 11 years after planting are positive: having compared the traditional reforestation techniques, plant biodiversity using the Miyawaki method appears very high, and the new coenosis (plant community) was able to evolve without further operative support after planting. Therefore, the implementation of supplementary technique along with cost reduction might provide a new and innovative tool to foresters and ecological engineering experts for Mediterranean environmental reforestation program.
Replanting native vegetation is a broadly accepted method for restoring degraded landscapes. Traditionally, seed used for restoration has been locally sourced to avoid introducing maladapted plants and to minimize the risk of outbreeding depression. However local adaptation is not universal and is disrupted by, for example, climate change and habitat fragmentation. We established a common garden experiment of ca. 1500 seedlings sourced from one local and two non-local provenances of Eucalyptus leucoxylon to test whether local provenancing was appropriate. The three provenances spanned an aridity gradient, with the local provenance sourced from the most mesic area. We explored the effect of provenance on four fitness proxies after 15 months, including survival, above-ground height, susceptibility to insect herbivory, and pathogen related stress. The local provenance had the highest mortality and grew least. The local provenance also suffered most from invertebrate herbivory and pathogen related stress. These results provide evidence that no advantage would be gained during the establishment of Eucalyptus leucoxylon at this site by using only the local provenance from within the range we sampled. Our results suggest that incorporating more diverse seed mixes from across the aridity gradient during the restoration of Eucalyptus leucoxylon open woodlands would provide quantifiable benefits to restoration (e.g. 6–10% greater survival, 20–25% greater plant height, 16–45% more pathogen resistance during establishment). We demonstrated these restoration gains by embedding a common garden experiments into a restoration project, and we recommend this approach be more widely adopted because it provides an effective way to facilitate adaptive management options for restoration stakeholders based on empirical evidence.
Human-driven changes in the global environment pose an increasingly urgent challenge for the management of ecosystems that is made all the more difficult by the uncertain future of both environmental conditions and ecological responses. Land managers need strategies to increase regional adaptive capacity, but relevant and rapid assessment approaches are lacking. To address this need, we developed a method to assess regional protected area networks across biophysically important climatic gradients often linked to biodiversity and ecosystem function. We plot the land of the southwestern United States across axes of historical climate space, and identify landscapes that may serve as strategic additions to current protected area portfolios. Considering climate space is straightforward, and it can be applied using a variety of relevant climate parameters across differing levels of land protection status. The resulting maps identify lands that are climatically distinct from existing protected areas, and may be utilized in combination with other ecological and socio-economic information essential to collaborative landscape-scale decision-making. Alongside other strategies intended to protect species of special concern, natural resources, and other ecosystem services, the methods presented herein provide another important hedging strategy intended to increase the adaptive capacity of protected area networks.
The Kyoto Protocol (KP) requires signatories to reduce CO2-equivalent emissions by an average of 5.2% from 1990 levels by the commitment period 2008–2012. This constitutes only a small proportion of global greenhouse gas emissions. Importantly, countries can attain a significant portion of their targets by sequestering carbon in terrestrial ecosystems in lieu of emission reductions. Since carbon sink activities lead to ephemeral carbon storage, forest management and other activities that enhance carbon sinks enable countries to buy time as they develop emission reduction technologies. Although many countries are interested in sink activities because of their presumed low cost, the analysis in this paper suggests otherwise. While potentially a significant proportion of required CO2 emission reductions can be addressed using carbon sinks, it turns out that, once the opportunity cost of land and the ephemeral nature of sinks are taken into account, costs of carbon uptake could be substantial. Carbon uptake via forest activities varies substantially depending on location (tropical, Great Plains, etc.), activity (forest conservation, tree planting, management, etc.), and the assumptions and methods upon which the cost estimates are based. Once one eliminates forestry projects that should be pursued because of their biodiversity and other non-market benefits, or because of their commercial profitability, there remain few projects that can be justified purely on the grounds that they provide carbon uptake benefits.
Ecosystems provide important services that can help people adapt to climate variability and change. Recognizing this role of ecosystems, several international and nongovernmental organizations have promoted an ecosystem-based approach to adaptation. We review the scientific literature related to EbA (ecosystem-based adaptation) with forests and trees, and highlight five cases in which forests and trees can support adaptation: (1) forests and trees providing goods to local communities facing climatic threats; (2) trees in agricultural fields regulating water, soil, and microclimate for more resilient production; (3) forested watersheds regulating water and protecting soils for reduced climate impacts; (4) forests protecting coastal areas from climate-related threats; and (5) urban forests and trees regulating temperature and water for resilient cities. The literature provides evidence that ecosystem-based adaptation with forests and trees can reduce social vulnerability to climate hazards; however, uncertainties and knowledge gaps remain, particularly for regulating services in watersheds and coastal areas. Few studies have been undertake non ecosystem-based adaptation specifically, but the abundant literature on ecosystem services can be used to fill knowledge gaps. Many studies assess the multiple benefits of ecosystems for human adaptation or well-being, but also recognize trade-offs between ecosystem services. Better understanding is needed of the efficiency, costs, and benefits, and trade-offs of ecosystem-based adaptation with forests and trees. Pilot projects under implementation could serve as learning sites and existing information could be systematized and revisited with a climate change adaptation lens.
Using forests to mitigate climate change has gained much interest in science and policy discussions. We examine the evidence for carbon benefits, environmental and monetary costs, risks and trade-offs for a variety of activities in three general strategies: (1) land use change to increase forest area (afforestation) and avoid deforestation; (2) carbon management in existing forests; and (3) the use of wood as biomass energy, in place of other building materials, or in wood products for carbon storage. We found that many strategies can increase forest sector carbon mitigation above the current 162–256 Tg C/yr, and that many strategies have co-benefits such as biodiversity, water, and economic opportunities. Each strategy also has trade-offs, risks, and uncertainties including possible leakage, permanence, disturbances, and climate change effects. Because ∼60% of the carbon lost through deforestation and harvesting from 1700 to 1935 has not yet been recovered and because some strategies store carbon in forest products or use biomass energy, the biological potential for forest sector carbon mitigation is large. Several studies suggest that using these strategies could offset as much as 10–20% of current U.S. fossil fuel emissions. To obtain such large offsets in the United States would require a combination of afforesting up to one-third of cropland or pastureland, using the equivalent of about one-half of the gross annual forest growth for biomass energy, or implementing more intensive management to increase forest growth on one-third of forestland. Such large offsets would require substantial trade-offs, such as lower agricultural production and non-carbon ecosystem services from forests. The effectiveness of activities could be diluted by negative leakage effects and increasing disturbance regimes. Because forest carbon loss contributes to increasing climate risk and because climate change may impede regeneration following disturbance, avoiding deforestation and promoting regeneration after disturbance should receive high priority as policy considerations. Policies to encourage programs or projects that influence forest carbon sequestration and offset fossil fuel emissions should also consider major items such as leakage, the cyclical nature of forest growth and regrowth, and the extensive demand for and movement of forest products globally, and other greenhouse gas effects, such as methane and nitrous oxide emissions, and recognize other environmental benefits of forests, such as biodiversity, nutrient management, and watershed protection. Activities that contribute to helping forests adapt to the effects of climate change, and which also complement forest carbon storage strategies, would be prudent.
Ecosystem services are typically valued for their immediate material or cultural benefits to human wellbeing, supported by regulating and supporting services. Under climate change, with more frequent stresses and novel shocks, ‘climate adaptation services’, are defined as the benefits to people from increased social ability to respond to change, provided by the capability of ecosystems to moderate and adapt to climate change and variability. They broaden the ecosystem services framework to assist decision makers in planning for an uncertain future with new choices and options. We present a generic framework for operationalising the adaptation services concept. Four steps guide the identification of intrinsic ecological mechanisms that facilitate the maintenance and emergence of ecosystem services during periods of change, and so materialise as adaptation services. We applied this framework for four contrasted Australian ecosystems. Comparative analyses enabled by the operational framework suggest that adaptation services that emerge during trajectories of ecological change are supported by common mechanisms: vegetation structural diversity, the role of keystone species or functional groups, response diversity and landscape connectivity, which underpin the persistence of function and the reassembly of ecological communities under severe climate change and variability. Such understanding should guide ecosystem management towards adaptation planning.
The rehabilitation and restoration of land is a key strategy to recover services -goods and resources- ecosystems offer to the humankind. This paper reviews key examples to understand the superior effect of nature-based solutions to enhance the sustainability of catchment systems by promoting desirable soil and landscape functions. The use of concepts such as connectivity and the theory of system thinking framework allowed to review coastal and river management as a guide to evaluate other strategies to achieve sustainability. In land management, NBSs are not mainstream management. Through a set of case studies: organic farming in Spain; rewilding in Slovenia; land restoration in Iceland, sediment trapping in Ethiopia and wetland construction in Sweden, we show the potential of nature-based solutions (NBSs) as a cost-effective long term solution for hydrological risks and land degradation. NBSs can be divided into two main groups of strategies: soil solutions and landscape solutions. Soil solutions aim to enhance the soil health and soil functions through which local ecosystem services will be maintained or restored. Landscape solutions mainly focus on the concept of connectivity. Making the landscape less connected, facilitating less rainfall to be transformed into runoff and therefore reducing flood risk, increasing soil moisture and reducing droughts and soil erosion we can achieve the sustainability. The enhanced ecosystem services directly feed into the realization of the Sustainable Development Goals of the United Nations.
We reviewed the experimental evidence for long-term carbon (C) sequestration in soils as consequence of specific forest management strategies. Utilization of terrestrial C sinks alleviates the burden of countries which are committed to reducing their greenhouse gas emissions. Land-use changes such as those which result from afforestation and management of fast-growing tree species, have an immediate effect on the regional rate of C sequestration by incorporating carbon dioxide (CO2) in plant biomass. The potential for such practices is limited in Europe by environmental and political constraints. The management of existing forests can also increase C sequestration, but earlier reviews found conflicting evidence regarding the effects of forest management on soil C pools. We analyzed the effects of harvesting, thinning, fertilization application, drainage, tree species selection, and control of natural disturbances on soil C dynamics. We focused on factors that affect the C input to the soil and the C release via decomposition of soil organic matter (SOM). The differentiation of SOM into labile and stable soil C fractions is important. There is ample evidence about the effects of management on the amount of C in the organic layers of the forest floor, but much less information about measurable effects of management on stable C pools in the mineral soil. The C storage capacity of the stable pool can be enhanced by increasing the productivity of the forest and thereby increasing the C input to the soil. Minimizing the disturbances in the stand structure and soil reduces the risk of unintended C losses. The establishment of mixed species forests increases the stability of the forest and can avoid high rates of SOM decomposition. The rate of C accumulation and its distribution within the soil profile differs between tree species. Differences in the stability of SOM as a direct species effect have not yet been reported.