Carbon prospecting in tropical forests for climate change mitigation

Charting the future of high forest low deforestation jurisdictions

High forest low deforestation jurisdictions (HFLDs) contain many of the world's last intact forests with historically low deforestation. Since carbon financing typically uses historical deforestation rates as baselines, HFLDs facing the prospect of future threats may receive insufficient incentives to be protected. We found that from 2002 to 2020, HFLDs (n = 310) experienced 44% higher deforestation rates than their historical baselines, and 60 HFLDs underwent periods of high deforestation (deforestation rate > 0.501%) at 0.983 ± 0.649% (mean ± SD)-a rate 7.5 times higher than the 10-y historical baseline of all HFLDs. For HFLDs to receive sufficient carbon finance requires baselines that can better reflect future deforestation trajectories of HFLDs. Using an empirical multifactorial model, we show that most contemporary HFLDs are expected to undergo higher deforestation from 2020 to 2038 than their historical baselines, with 72 HFLDs likely (>66% probability) to undergo high deforestation. Over the next 18 y, HFLDs are expected to lose 2.16 Mha y-1 of forests corresponding to 585 ± 74 MtCO2e y-1 (mean ± SE) of emissions. Efforts to protect HFLD forests from future threats will be crucial. In particular, improving baselining methods is key to ensuring that sufficient financing can flow to HFLDs to prevent deforestation.

Conservation opportunities through improved management of recently established protected areas in Southeast Asia

Protected areas (PAs) play a crucial role in biodiversity conservation and climate change mitigation.1,2 However, ineffective management can lead to biodiversity loss and carbon emissions from deforestation.3,4,5,6 To address this issue and explore viable solutions, we assessed the impact of PA establishment on avoided deforestation in 80 Southeast Asian PAs using the synthetic control approach.7,8 Our results show that 36 PAs successfully prevented 78,910 ha of deforestation. However, the remaining 44 PAs lost 72,497 ha of forest, impacting the habitat of 226 threatened bird and mammal species. Effective management of these reserves could have potentially avoided up to 2.07 MtCO2e yr-1 in carbon emissions. We estimate that at least $17 million USD per year in additional funding is required to better manage these 44 ineffective PAs and reduce future emissions. Furthermore, we demonstrate that carbon markets have the potential to generate these funds by reducing carbon emissions from deforestation within protected areas. Our findings emphasize that improving PA management is an essential nature-based solution for conserving biodiversity and mitigating climate change.

Accounting for deep soil carbon in tropical forest conservation payments

Secondary tropical forests are at the forefront of deforestation pressures. They store large amounts of carbon, which, if compensated for to avoid net emissions associated with conversion to non-forest uses, may help advance tropical forest conservation. We measured above- and below-ground carbon stocks down to 1 m soil depth across a secondary forest and in oil palm plantations in Malaysia. We calculated net carbon losses when converting secondary forests to oil palm plantations and estimated payments to avoid net emissions arising from land conversion to a 22-year oil palm rotation, based on land opportunity costs per hectare. We explored how estimates would vary between forests by also extracting carbon stock data for primary forest from the literature. When tree and soil carbon was accounted for, payments of US$18-51 tCO2-1 for secondary forests and US$14-40 tCO2-1 for primary forest would equal opportunity costs associated with oil palm plantations per hectare. If detailed assessments of soil carbon were not accounted for, payments to offset opportunity costs would need to be considerably higher for secondary forests (US$28-80 tCO2-1). These results show that assessment of carbon stocks down to 1 m soil depth in tropical forests can substantially influence the estimated value of avoided-emission payments.

Two centuries of biodiversity discovery and loss in Singapore

There is an urgent need for reliable data on the impacts of deforestation on tropical biodiversity. The city-state of Singapore has one of the most detailed biodiversity records in the tropics, dating back to the turn of the 19th century. In 1819, Singapore was almost entirely covered in primary forest, but this has since been largely cleared. We compiled more than 200 y of records for 10 major taxonomic groups in Singapore (>50,000 individual records; >3,000 species), and we estimated extinction rates using recently developed and novel statistical models that account for "dark extinctions," i.e., extinctions of undiscovered species. The estimated overall extinction rate was 37% (95% CI [31 to 42%]). Extrapolating our Singapore observations to a future business-as-usual deforestation scenario for Southeast Asia suggests that 18% (95% CI [16 to 22%]) of species will be lost regionally by 2100. Our extinction estimates for Singapore and Southeast Asia are a factor of two lower than previous estimates that also attempted to account for dark extinctions. However, we caution that particular groups such as large mammals, forest-dependent birds, orchids, and butterflies are disproportionately vulnerable.

Confronting deep uncertainty in the forest carbon industry

Resilience-based and service-focused approaches could reduce contentions and injustices.

Enabling Future Closed-Loop Recycling of Spent Lithium-Ion Batteries: Direct Cathode Regeneration

The rapid proliferation of electric vehicles equipped with lithium-ion batteries (LIBs) presents serious waste management challenges and environmental hazards for recyclers after scrap. Closed-loop recycling contributes to the sustainable development of batteries and plays an important role in mitigating raw material shortages and supply chain risks. Herein, current direct cathode regeneration methods for industrialized recycling are outlined and evaluated. Different regeneration methods for spent cathode materials are summarized, which provide a new perspective for realizing closed-loop recycling of LIBs. A reference recycling route for retrofitting existing cathode production lines is proposed and minimizes the costs. In addition to promoting the industrialization of direct cathode recycling, the environmental, economic, and political benefits of battery recycling are also highlighted.

Variations of methane fluxes and methane microbial community composition with soil depth in the riparian buffer zone of a sponge city park

Riparian buffers benefit both natural and man-made ecosystems by preventing soil erosion, retaining soil nutrients, and filtering pollutants. Nevertheless, the relationship between vertical methane fluxes, soil carbon, and methane microbial communities in riparian buffers remains unclear. This study examined vertical methane fluxes, soil carbon, and methane microbial communities in three different soil depths (0-5 cm, 5-10 cm, and 10-15 cm) within a riparian buffer of a Sponge City Park for one year. Structural equation model (SEM) results demonstrated that vertical methane fluxes varied with soil depths (λ = -0.37) and were primarily regulated by methanogenic community structure (λ = 0.78). Notably, mathematical regression results proposed that mcrA/pmoA ratio (R² = 0.8) and methanogenic alpha diversity/methanotrophic alpha diversity ratio (R² = 0.8) could serve as valid predictors of vertical variation in methane fluxes in the riparian buffer of urban river. These findings suggest that vertical variation of methane fluxes in riparian buffer soils is mainly influenced by carbon inputs and methane microbial abundance and community diversity. The study's results quantitatively the relationship between methane fluxes in riparian buffer soils and abiotic and biotic factors in the vertical direction, therefore contributing to the further development of mathematical models of soil methane emissions.

Future carbon storages of ecosystem based on land use change and carbon sequestration practices in a large economic belt

Assessments of ecosystem carbon storage are needed to form the scientific basis for carbon policies. Due to lack of data, there are few accurate, large-scale, and long-term predictions of ecosystem carbon storage. This study used the Distributed Land-Use Change Prediction (DLUCP) model with ten socioeconomic and two climate change scenarios for a total of 20 combinations that take into account population increase, technology innovation, climate change, and Grain for Green Project to make high-resolution predictions of land use change in the Yangtze River Economic Belt. Low and high carbon sequestration practices were considered to predict future carbon densities. Land use change data, carbon densities data, and the InVEST model were used to predict changes in ecosystem carbon storage from now to 2070. The results show a slight increase (1.88-4.17%) in carbon storage in the study area only based on land use change. Grain for Green Project has the largest impact on carbon storage among population increase, technology innovation, climate scenarios, and Grain for Green Project, which increases carbon storage by 4.17%. After the implementation of carbon sequestration practices, there is an increase in carbon storages from 28.51 to 56.77% in the study area from now to 2070, and increasing carbon storages of forest in each stream and carbon storage of cropland in downstream are efficient ways to achieve carbon neutralization.

Climate co-benefits of tiger conservation

Biodiversity conservation is increasingly being recognized as an important co-benefit in climate change mitigation programmes that use nature-based climate solutions. However, the climate co-benefits of biodiversity conservation interventions, such as habitat protection and restoration, remain understudied. Here we estimate the forest carbon storage co-benefits of a national policy intervention for tiger (Panthera tigris) conservation in India. We used a synthetic control approach to model avoided forest loss and associated carbon emissions reductions in protected areas that underwent enhanced protection for tiger conservation. Over a third of the analysed reserves showed significant but mixed effects, where 24% of all reserves successfully reduced the rate of deforestation and the remaining 9% reported higher-than-expected forest loss. The policy had a net positive benefit with over 5,802 hectares of averted forest loss, corresponding to avoided emissions of 1.08 ± 0.51 MtCO2 equivalent between 2007 and 2020. This translated to US$92.55 ± 43.56 million in ecosystem services from the avoided social cost of emissions and potential revenue of US$6.24 ± 2.94 million in carbon offsets. Our findings offer an approach to quantitatively track the carbon sequestration co-benefits of a species conservation strategy and thus help align the objectives of climate action and biodiversity conservation.

Broadening the focus of forest conservation beyond carbon

Two concurrent trends are contributing towards a much broader view of forest conservation. First, the appreciation of the role of forests as a nature-based climate solution has grown rapidly, particularly among governments and the private sector. Second, the spatiotemporal resolution of forest mapping and the ease of tracking forest changes have dramatically improved. As a result, who does and who pays for forest conservation is changing: sectors and people previously considered separate from forest conservation now play an important role and need to be held accountable and motivated or forced to conserve forests. This change requires, and has stimulated, a broader range of forest conservation solutions. The need to assess the outcomes of conservation interventions has motivated the development and application of sophisticated econometric analyses, enabled by high resolution satellite data. At the same time, the focus on climate, together with the nature of available data and evaluation methods, has worked against a more comprehensive view of forest conservation. Instead, it has encouraged a focus on trees as carbon stores, often leaving out other important goals of forest conservation, such as biodiversity and human wellbeing. Even though both are intrinsically connected to climate outcomes, these areas have not kept pace with the scale and diversification of forest conservation. Finding synergies between these 'co-benefits', which play out on a local scale, with the carbon objective, related to the global amount of forests, is a major challenge and area for future advances in forest conservation.

The threat of COVID-19 to the conservation of Tanzanian national parks

In many low-income countries, the conservation of natural resources in protected areas relies on tourism revenue. However, tourist numbers in Africa were severely reduced by the COVID-19 pandemic, thus, putting the conservation of these important protected areas at risk. We use records from gate passings at national parks across Tanzania to demonstrate the immediate and severe impact on tourist numbers and revenues resulting from the COVID-19 pandemic and associated restrictions, and whether international and local (East African) tourists were affected equally. We discuss mechanisms that may reduce future negative impacts of sudden loss of revenue from international tourism, such as increasing the revenue portfolio and thereby decrease the dependency on revenues from international tourists. More important, we encourage local governments, national park authorities, and the world community to further develop and initiate external funding options to reduce the dependency on income from international nature-based tourism to preserve national parks and biodiversity. An additional long-term goal for ensuring sustained conservation would be to increase benefits to local communities adjacent to national parks, encouraging local involvement and thereby reducing the dependence on external funding in the future.

Boost the resilience of protected areas to shocks by reducing their dependency on tourism

Ecotourism is widely considered a strong mechanism for the sustainable funding of protected areas (PAs). Implemented during the 1990s in Madagascar, nature-based tourism experienced positive growth over the last 30 years with increasing numbers of visits to the parks and reserves. Revenue earned from entrance fees to the network of PAs managed by Madagascar National Parks has never been sufficient to finance their management. Political crises and the COVID-19 pandemic in particular, have highlighted for park managers, the risk of relying on such earnings when they covered just 1% of the required funding in 2021. Alternative mechanisms of funding are analysed for all of Madagascar's PAs with a view to facilitating sustainable conservation of the localities and protection of the island's biodiversity.

Future land-use competition constrains natural climate solutions

Natural climate solutions (NCS) are an essential complement to climate mitigation and have been increasingly incorporated into international mitigation strategies. Yet, with the ongoing population growth, allocating natural areas for NCS may compete with other socioeconomic priorities, especially urban development and food security. Here, we projected the impacts of land-use competition incurred by cropland and urban expansion on the climate mitigation potential of NCS. We mapped the areas available for implementing 9 key NCS strategies and estimated their climate change mitigation potential. Then, we overlaid these areas with future cropland and urban expansion maps projected under three Shared Socioeconomic Pathway (SSP) scenarios (2020-2100) and calculated the resulting mitigation potential loss of each selected NCS strategy. Our results estimate a substantial reduction, 0.3-2.8 GtCO₂ yr^-1 or 4-39 %, in NCS mitigation potential, of which cropland expansion for fulfilling future food demand is the primary cause. This impact is particularly severe in the tropics where NCS hold the most abundant mitigation potential. Our findings highlight immediate actions prioritized to tropical areas are important to best realize NCS and are key to developing realistic and sustainable climate policies.

Gains in biodiversity conservation and ecosystem services from the expansion of the planet's protected areas

Protected areas safeguard biodiversity, ensure ecosystem functioning, and deliver ecosystem services to communities. However, only ~16% of the world's land area is under some form of protection, prompting international calls to protect at least 30% by 2030. We modeled the outcomes of achieving this 30 × 30 target for terrestrial biodiversity conservation, climate change mitigation, and nutrient regulation. We find that the additional ~2.8 million ha of habitat that would be protected would benefit 1134 ± 175 vertebrate species whose habitats currently lack any form of protection, as well as contribute to either avoided carbon emissions or carbon dioxide sequestration, equivalent to 10.9 ± 3.6 GtCO₂ year^-1 (28.4 ± 9.4% of the global nature-based climate-change mitigation potential). Furthermore, expansion of the protected area network would increase its ability to regulate water quality and mitigate nutrient pollution by 142.5 ± 31.0 MtN year^-1 (28.5 ± 6.2% of the global nutrient regulation potential).

Aboveground carbon accumulation by second-growth forests after deforestation in Hawai'i

Successional processes ultimately determine and define carbon accumulations in forested ecosystems. Although primary succession on wholly new substrate occurs across the globe, secondary succession, often following storm events or anthropogenic disturbance, is more common and is capable of globally significant accumulations of carbon (C) at a time when offsets to anthropogenic carbon dioxide (CO₂ ) emissions are critically needed. In Hawai'i, prior studies have investigated ecosystem development during primary succession on lava flows, including estimates of C mass accumulation. Yet relatively little is known regarding secondary succession of Hawaii's native forests, particularly regarding C mass accumulation. Here we documented aboveground C mass accumulation by native- and nonnative-dominated second-growth forests following deforestation of mature native lowland rainforests in the Puna District of Hawai'i Island. We characterized species composition and stand structure of three distinct successional forest stand types: those dominated by the native tree, Metrosideros polymorpha ('Ōhi'a), and those dominated by invasive nonnative trees, Falcataria moluccana (albizia) and Psidium cattleianum (strawberry guava). We compared M. polymorpha-dominated and F. moluccana-dominated second-growth forests to adjacent mature M. polymorpha-dominated forests as well as young M. polymorpha-dominated forests undergoing initial stages of primary succession on 36-years-old lava fields. Aboveground carbon density (ACD) values of mature primary forest stands (171 Mg/ha) were comparable to those of mature continental tropical forests. M. polymorpha-dominated second-growth stands attained nearly 50% of ACD values of mature primary forests after less than 30 years of post-disturbance succession and exhibited aboveground carbon accumulation rates of ~3 Mg C·ha^-1 ·year^-1 . Such rates were comparable to those of second-growth forests in continental tropics. Rates of ACD accumulation by second-growth forests dominated by nonnative F. moluccana stands were similar, or slightly greater than, those of M. polymorpha-dominated stands. However, M. polymorpha individuals were virtually absent from stands dominated by either P. cattleianum or F. moluccana. Taken together, results demonstrated that re-establishment and rapid accumulation of C mass by M. polymorpha stands during secondary succession is certainly possible, but only where populations of nonnative species have not already colonized areas during early stages of secondary succession.

Spatiotemporal Evolution and Influencing Factors of Carbon Sink Dynamics at County Scale: A Case Study of Shaanxi Province, China

To explore the spatiotemporal evolution of carbon sinks in Shaanxi Province, and their impact mechanisms, this study used panel data from 107 counties (districts) in Shaanxi Province from 2000 to 2017. First, we conducted spatial distribution directional analysis and exploratory spatial data analysis (ESDA). Then, we constructed a geographic spatial weight matrix and used the spatial panel Durbin model to analyze the driving factors of carbon sink changes in Shaanxi Province, from the perspective of spatial effects. The results showed that: (1) The temporal evolution of carbon sinks during the study period showed an overall upward trend, but the carbon sinks of counties (districts) differed greatly, and the center of gravity of carbon sinks, as a whole, showed the characteristics of “south to north” migration. (2) The carbon sinks of Shaanxi Province have a significant positive global spatial autocorrelation in geographic space. The local spatial pattern was characterized by low-value agglomeration (low-low cluster) and high-value agglomeration (high-high cluster), supplemented by high-value bulge (high-low outlier) and low-value collapse (low-high outlier). (3) The result of the spatial measurement model proved that the spatial Durbin model, with dual fixed effects of time and space, should be selected. In the model results, factors such as population, per capita gross domestic product (GDP), local government general budget expenditure, and local government general budget revenue all reflect strong spatial spillover effects. Accordingly, in the process of promoting “carbon neutrality”, the government needs to comprehensively consider the existence of spatial spillover effects between neighboring counties (districts), and strengthen the linkage-management and control roles of counties (districts) in increasing carbon sinks.