How do we best synergize climate mitigation actions to co-benefit biodiversity?

Perspectives on the timing of ecosystem collapse in a changing climate

Climate change is one of the most important drivers of ecosystem change, the global-scale impacts of which will intensify over the next 2 decades. Estimating the timing of unprecedented changes is not only challenging but is of great importance for the development of ecosystem conservation guidelines. Time of emergence (ToE) (point at which climate change can be differentiated from a previous climate), a widely applied concept in climatology studies, provides a robust but unexplored approach for assessing the risk of ecosystem collapse, as described by the C criterion of the International Union for Conservation of Nature's Red List of Ecosystems (RLE). We identified 3 main theoretical considerations of ToE for RLE assessment (degree of stability, multifactorial instead of one-dimensional analyses, and hallmarks of ecosystem collapse) and 4 sources of uncertainty when applying ToE methodology (intermodel spread, historical reference period, consensus among variables, and consideration of different scenarios), which aims to avoid misuse and errors while promoting a proper application of the framework by scientists and practitioners. The incorporation of ToE for the RLE assessments adds important information for conservation priority setting that allows prediction of changes within and beyond the time frames proposed by the RLE.

Wilder rangelands as a natural climate opportunity: Linking climate action to biodiversity conservation and social transformation

Rangelands face threats from climate and land-use change, including inappropriate climate change mitigation initiatives such as tree planting in grassy ecosystems. The marginalization and impoverishment of rangeland communities and their indigenous knowledge systems, and the loss of biodiversity and ecosystem services, are additional major challenges. To address these issues, we propose the wilder rangelands integrated framework, co-developed by South African and European scientists from diverse disciplines, as an opportunity to address the climate, livelihood, and biodiversity challenges in the world's rangelands. More specifically, we present a Theory of Change to guide the design, monitoring, and evaluation of wilder rangelands. Through this, we aim to promote rangeland restoration, where local communities collaborate with regional and international actors to co-create new rangeland use models that simultaneously mitigate the impacts of climate change, restore biodiversity, and improve both ecosystem functioning and livelihoods.

Interconnecting global threats: climate change, biodiversity loss, and infectious diseases

The concurrent pressures of rising global temperatures, rates and incidence of species decline, and emergence of infectious diseases represent an unprecedented planetary crisis. Intergovernmental reports have drawn focus to the escalating climate and biodiversity crises and the connections between them, but interactions among all three pressures have been largely overlooked. Non-linearities and dampening and reinforcing interactions among pressures make considering interconnections essential to anticipating planetary challenges. In this Review, we define and exemplify the causal pathways that link the three global pressures of climate change, biodiversity loss, and infectious disease. A literature assessment and case studies show that the mechanisms between certain pairs of pressures are better understood than others and that the full triad of interactions is rarely considered. Although challenges to evaluating these interactions-including a mismatch in scales, data availability, and methods-are substantial, current approaches would benefit from expanding scientific cultures to embrace interdisciplinarity and from integrating animal, human, and environmental perspectives. Considering the full suite of connections would be transformative for planetary health by identifying potential for co-benefits and mutually beneficial scenarios, and highlighting where a narrow focus on solutions to one pressure might aggravate another.

Over 1/4 of China's terrestrial area significantly contributed both to biodiversity conservation and carbon neutrality, requiring protection

Protected areas (PAs) play a crucial role in halting biodiversity loss and mitigating climate change. However, research on the advantages of integrating biodiversity conservation and climate mitigation within PAs remains limited, and there is a deficiency in holistic, scientifically supported management strategies. To address these gaps, we conducted a case study in China, comparing the conservation effectiveness of designating conservation priorities considering either single or multiple objectives, including biodiversity conservation and carbon neutrality. The results showed that integrating multiple values could truly increase the effectiveness of PAs compared to a single value considered. Over 1/4 of China's terrestrial area had a significant contribution for both biodiversity conservation and carbon neutrality, yet remained unprotected. Expanding PAs in these areas holds tremendous win-win biodiversity conservation and carbon neutrality opportunity. We delineated different conservation priorities for comprehensive management and outlined strategies for different types of areas. The framework presented in this study can serve as a reference for other places with comparable scales or management objectives.

Is tree planting an effective strategy for climate change mitigation?

The world's forests store large amounts of carbon (C), and growing forests can reduce atmospheric CO2 by storing C in their biomass. This has provided the impetus for world-wide tree planting initiatives to offset fossil-fuel emissions. However, forests interact with their environment in complex and multifaceted ways that must be considered for a balanced assessment of the value of planting trees. First, one needs to consider the potential reversibility of C sequestration in trees through either harvesting or tree death from natural factors. If carbon storage is only temporary, future temperatures will actually be higher than without tree plantings, but cumulative warming will be reduced, contributing both positively and negatively to future climate-change impacts. Alternatively, forests could be used for bioenergy or wood products to replace fossil-fuel use which would obviate the need to consider the possible reversibility of any benefits. Forests also affect the Earth's energy balance through either absorbing or reflecting incoming solar radiation. As forests generally absorb more incoming radiation than bare ground or grasslands, this constitutes an important warming effect that substantially reduces the benefit of C storage, especially in snow-covered regions. Forests also affect other local ecosystem services, such as conserving biodiversity, modifying water and nutrient cycles, and preventing erosion that could be either beneficial or harmful depending on specific circumstances. Considering all these factors, tree plantings may be beneficial or detrimental for mitigating climate-change impacts, but the range of possibilities makes generalisations difficult. Their net benefit depends on many factors that differ between specific circumstances. One can, therefore, neither uncritically endorse tree planting everywhere, nor condemn it as counter-productive. Our aim is to provide key information to enable appropriate assessments to be made under specific circumstances. We conclude our discussion by providing a step-by-step guide for assessing the merit of tree plantings under specific circumstances.

Environmental problem shifting from climate change mitigation: A mapping review

Climate change mitigation will trigger major changes in human activity, energy systems, and material use, potentially shifting pressure from climate change to other environmental problems. We provide a comprehensive overview of such "environmental problem shifting" (EPS). While there is considerable research on this issue, studies are scattered across research fields and use a wide range of terms with blurred conceptual boundaries, such as trade-off, side effect, and spillover. We identify 506 relevant studies on EPS of which 311 are empirical, 47 are conceptual-theoretical, and 148 are synthetic studies or reviews of a particular mitigation option. A systematic mapping of the empirical studies reveals 128 distinct shifts from 22 categories of mitigation options to 10 environmental impacts. A comparison with the recent IPCC report indicates that EPS literature does not cover all mitigation options. Moreover, some studies systematically overestimate EPS by not accounting for the environmental benefits of reduced climate change. We propose to conceptually clarify the different ways of estimating EPS by distinguishing between gross, net, and relative shifting. Finally, the ubiquity of EPS calls for policy design which ensures climate change mitigation that minimizes unsustainability across multiple environmental dimensions. To achieve this, policymakers can regulate mitigation options-for example, in their choice of technology or location-and implement complementary environmental policies.

How to synergize ecological restoration to co-benefit the beneficial contributions of nature to people on the Qinghai-Tibet Plateau?

Understanding the magnitude and spatial distribution of ecological restoration requires a precise assessment of the beneficial contributions of nature to people. However, where the restoration areas should be located and whether the natural contribution of a compensation area can satisfy people's needs in the context of ecological degradation remain unclear. To address these issues, we selected the Qinghai-Tibet Plateau as the study areas, utilizing the offset portfolio analyzer and locator model to identify the compensation sites that offset the losses of ecosystem services and biodiversity resulting from ecological degradation. These compensation sites were developed through two offset types: restoration and protection. Then, based on the offset sites, we assessed nature's contribution to people (NCP) under the current status and future scenarios in terms of various aspects, including the habitat (NCP1), climate change (NCP4), and water quantity and flow regulation (NCP6). This study found that the area impacted by agricultural development was 7.15 × 105 ha, and the required compensation area was 5.5 × 106 ha under the current status. The ratio of the impacted area to the required area was approximately 7.0 in the future scenarios. The average habitat qualities were 0.14 and 0.30, while the mean NCP1 values were 2.69 and 0.51 in the protection and restoration offset sites, respectively. Moreover, based on the offset sites, the high-value contributions in NCP4 accounted for 18.64%-22.69% and 38.87%-46.17% of the total offset sites in terms of the restoration and protection offset types, respectively. Additionally, the estimated high-value contributions in NCP6 accounted for 58.35%-59.02% and 84.40%-95.86% of the total offset sites in the restoration and protection offset types, respectively. Our findings highlighted the significance of ecological restoration in showcasing the role of NCPs. These results could aid conservation managers in developing more targeted ecological strategies to enhance human well-being.

Overcoming the coupled climate and biodiversity crises and their societal impacts

Earth's biodiversity and human societies face pollution, overconsumption of natural resources, urbanization, demographic shifts, social and economic inequalities, and habitat loss, many of which are exacerbated by climate change. Here, we review links among climate, biodiversity, and society and develop a roadmap toward sustainability. These include limiting warming to 1.5°C and effectively conserving and restoring functional ecosystems on 30 to 50% of land, freshwater, and ocean "scapes." We envision a mosaic of interconnected protected and shared spaces, including intensively used spaces, to strengthen self-sustaining biodiversity, the capacity of people and nature to adapt to and mitigate climate change, and nature's contributions to people. Fostering interlinked human, ecosystem, and planetary health for a livable future urgently requires bold implementation of transformative policy interventions through interconnected institutions, governance, and social systems from local to global levels.

Avoiding emissions versus creating sinks-Effectiveness and attractiveness to climate finance

The perception of greater impact via new sinks, as opposed to through avoided emissions, has already led some large investors to focus on sink-related projects. This is a flawed perception when applied universally and carries a risk that effective routes to mitigation through avoiding emissions are side-lined. In reality, both emissions avoidance and emissions removal are needed, and both can be a cost-effective means of delivering mitigation.

Biological mechanisms matter in contemporary wildlife conservation

Given limited resources for wildlife conservation paired with an urgency to halt declines and rebuild populations, it is imperative that management actions are tactical and effective. Mechanisms are about how a system works and can inform threat identification and mitigation such that conservation actions that work can be identified. Here, we call for a more mechanistic approach to wildlife conservation and management where behavioral and physiological tools and knowledge are used to characterize drivers of decline, identify environmental thresholds, reveal strategies that would restore populations, and prioritize conservation actions. With a growing toolbox for doing mechanistic conservation research as well as a suite of decision-support tools (e.g., mechanistic models), the time is now to fully embrace the concept that mechanisms matter in conservation ensuring that management actions are tactical and focus on actions that have the potential to directly benefit and restore wildlife populations.

The direct drivers of recent global anthropogenic biodiversity loss

Effective policies to halt biodiversity loss require knowing which anthropogenic drivers are the most important direct causes. Whereas previous knowledge has been limited in scope and rigor, here we statistically synthesize empirical comparisons of recent driver impacts found through a wide-ranging review. We show that land/sea use change has been the dominant direct driver of recent biodiversity loss worldwide. Direct exploitation of natural resources ranks second and pollution third; climate change and invasive alien species have been significantly less important than the top two drivers. The oceans, where direct exploitation and climate change dominate, have a different driver hierarchy from land and fresh water. It also varies among types of biodiversity indicators. For example, climate change is a more important driver of community composition change than of changes in species populations. Stopping global biodiversity loss requires policies and actions to tackle all the major drivers and their interactions, not some of them in isolation.