Optimal allocation of nature‐based solutions to achieve climate mitigation and adaptation goals

Read the free Plain Language Summary for this article on Journal blog. Global action is urgently needed to prevent further climate change and counteract negative impacts that causing people's wellbeing natural environment. Climate increasing prevalence of extreme temperatures weather events, having a significant toll lives (Bellprat et al., 2019; Herring 2014; Perkins-Kirkpatrick 2022). For instance, 37% heat-related deaths can be attributed anthropogenic (Vicedo-Cabrera 2021). Nature-based solutions (NbS) refer actions protect, manage restore ecosystems in ways also provide benefits people, are considered an alternative support mitigation adaptation goals (Seddon, Yet we lack full understanding diversity when implementing NbS. Application NbS mitigate centres protecting carbon stocks enhancing sequestration alteration current patterns, mostly through forest protection or restoration (GCF, 2020a; Seddon, Use aims decrease local vulnerability present by ecosystems' health their capacity sustain (i.e. ecosystem services; GCF, 2020b; example, Sri Lanka, project using focused improving sustainable farm- land management practices upstream erosion downstream flood risk 2020b). The importance both fighting has been widely recognized international policy, yet practical efforts date have largely only goal; 2021; UN, 2022; UNFCCC, Strong evidence suggests projects promote conservation may not enhance provision services, even adversely affect communities' (Aggarwal & Brockington, 2020; Chhatre Agrawal, 2009; Duker Kim 2018; Rana 2017). Therefore, there pressing need better understand how help achieve objectives cost-effectively allocate finite resources available objectives. Here, use spatial planning approach explore consequences different population sectors investing pursuing either goals, both. We evaluated people biophysical modelling monetary evaluation three regulating services. storage as representative service delivers global benefit stability. sediment retention goals. Previous work looking at application (Hu Khorchani Nolan consider implementation wider variety assess changes distribution population. applied our Kali Gandaki watershed Nepal, country with national-level commitments financing (Government 2016; MoFE, 2018). Topographical conditions make Nepal highly prone erosion, which expected intensify consequence 2020c; Manandhar 2012; Panthi 2016). specifically ask (1) How do services differs targeting versus goals?; (2) priority locations differ (3) To what extent strategies balance trade-offs cost? River originates from Mustang Plateau Chinese-Nepali border. study region watershed, covering 7600 km2 (Figure 1). basin variable geology, altitude ranging 525 8144 m (World Bank, 2019). holds great diversity, arid tundra highest altitudes, alpine, cold temperate, warm temperate subtropical climates decreasing monsoon lowest areas (Manandhar 2012). According 2011 national census, approximately 590,000 living 2013). Agriculture, grazing collection fuel wood main livelihoods region, 20% cover, grassland 14% cultivation Agriculture occurs lower however, agriculture occurring very steep slopes (with mean gradient 41%). high precipitation require most croplands converted elaborate system terraces control water hillslopes Terrace abandonment expansion road network without stabilization methods exacerbate levels Almost 22 million cubic metres transported Dam each year, resulting maintenance costs A Hydropower Plant (KGA hydropower plant; World KGA largest power plant installed 144MW, single generator (NEA, formulated decision problem identify (climate goal), Table 1), considering following beneficiaries: increase metric tons its regulation benefit, on-site sediment/year benefitting agricultural landholders plant. obtained modelled data Bank (2019), reflecting impact (Table 2). include hill terrace improvement, soil practices, rehabilitation forests grasslands. Modelled reflect difference between baseline landscape place hypothetical separately, bundles actions. Bundles included: + improvement rehabilitation, (4) rehabilitation. Each represents suite example accounts like slope correction, planting nitrogen-fixing species along margins agroforestry Hypothetical models account all listed under NbS, instead, average types incorporated into changing model parameters. details equations parameters used (after implementation) landscapes please see Supporting Information Text S1. were (2019). methodology obtain information included literature review (Atreya 2008; Dahal Bajracharya, 2013; ICIMOD, 2007; Paudel 2017; Shrestha, 2016), official reports Department Forests Soil Conservation, Government stakeholder consultation during two workshops held October 2017 January 2019 Kathmandu Costs gross initial establishment borne adopting practice. Labour calculated common daily wage rate US $3 per day, adjusted year (2018; multi-objective optimization find where apply them best this, area was divided 821 sub-watersheds size 900 ha each, roughly individual micro-watersheds Conservation typically addresses programs these represented ‘decision unit’, regions green could implemented. within unit based suitability layer (information review, workshops, (research question 1) constructed Pareto efficiency frontiers pairs representing set spatially explicit optimal returns one objective cannot increased diminishing another (Gourevitch Efficiency allowed us allocation differed across units Pairs combined weighted sum proportional increases decreases weight 1000 iterations, is, 100% 0% other objective. Solutions giving represent retention) integrated optimization, predefined allocations relative 3). Our (i) Mitigation strategy: gives sequestration, (ii) Adaptation distributes equally (iii) sediment. This compared proportion captured maximum given weight. then associated changed strategies. strategy goal) captures ~70% possible value respectively goals; Figure 2a). Conversely, loads locally goals), 56% 2b). same significantly objectives, capturing 93% storage, 96% 97% 2c). impacted specific goal pursued sediment) 95% S1). because amount reaching streams estimated load values (Supporting In strategy, selected (45% total number selected) followed (35%), improvements (20%) 3a). (57% selected), (41%) (2%). shifted (76% (17%) (7%). Decision located South strategies, although allocated North strategy. Despite configuration units, (15,700–17,000 ha), (0–5500 (0–2542) (307–321 ha; 3b). 39M benefits, figure, 38M restored retained 1M avoided 4). time goals) 23M benefits. 21M, 54% attainable. almost 2M, 37M 35M, 89% While remains near 2M. integrate agendas highlighted (IPCC, 2018, 2022a, 2022b; OECD, integration prominent policy practice (Hurlimann Green Fund, biggest mechanism supporting fight developing countries (https://www.greenclimate.fund/), evaluates separately 2020a, 2020d, Using prioritization, show miss more than 30% 40% benefiting globally. integrating 90% results highlight groups landscape, research identified healthy ecosystems, restoring cost-effective (Cook-Patton combination (including improved rehabilitation) necessary evenly Particularly, feasible effective align recent indicating terracing mountainous China (Chen 2020). Terracing systems thousands years, shown reduce 52% if adequately maintained (Deng due relatively low extension remaining cover Watershed, (155,300 ha) From 330 degraded therefore implement emphasize relevant according context order adaptation. traditional systems. Agroforestry while providing biodiversity cobenefits cases high-intensity hazards (e.g. storm cities), approaches technological engineering preferred Achieving requires careful consideration cultural social norms (Friedman Mashi Papua New Guinea, women men networks Understanding complexities key delivering prevention education campaigns improve responses emergencies events (Mashi measured terms function, translated terms. function intervention evaluations it processes dynamics fundamentally supports nature reductions loss, stocks, quality) (Chan Satterfield, However, translate funding mechanisms operate monetization nature. Carbon credits since 1997 adoption Kyoto Protocol (UN, 1998). Fund REED+ (Reducing emissions deforestation degradation countries) credits. exchange (equivalent ton greenhouse gases removed atmosphere) businesses developed pay offset gas 2015). Even though provided debated Jacobs Martin-Ortega 2019), creation funds indicates useful method assist private government action. did measure would appropriate data. reported cost-share similar estimate equivalent 84% cost. Considering 40M budget, 34M reduced form fertility, capture productivity takes hillslope susceptible exacerbated (Panthi Thus, helps adaptive farmers change. reducing avoid 2M USD de-sanding turbines maintaining reservoir Maintaining valuable flow insufficient meet electricity demands ensure likely become variability season acknowledge, valuations many receive Particularly nonmaterial connections shaped unique lenses (as term ‘nature's contributions people’ encompasses Díaz significance practicing (Salas Tillman, 2021) community perceptions indirect plants (Sousa Other required participatory mapping, focus groups, photograph analysis, among others Hirons Extraction sustenance provisioning out scope study. finding securing access consideration. Specifically light range demonstrating strict These considerations bolstered study's findings result realization considered. It important note interventions here conservative estimates. Himalayas, sources glaciation, mass-movement landslides rockfalls), sheet rill areas, river channels (Wasson, 2003). addition, activities construction mining (Sidle Ziegler, estimates loads, InVEST Sediment Delivery Ratio model, (Sharp subject limitations. assumes linear over does such photosynthesis rates presence organisms facilitate sequestration. affected neighbouring November 2022, United Nations Change Conference COP27, unprecedented Implementation Plan announced (UNFCCC, plan acknowledges experience greater loss damage infrastructure disasters previously recognized, urges financial Underlying urgent call recognition existing gap adverse experiencing today Vicedo-Cabrera provides pertinent timely development plans contribute capacities 2022); contribution small fossil fuels drastically cut down (Anderson On hand, currently annual capita emissions—only 0.59 Mt 2020, >12 20 (Crippa 2021)—have less potential but tremendous targets strategic incentivize policies Himalayan Region. Nepalese incentivized 50 interest institutions Paudyal Sharma distributed assumptions distributions budget implementation, budgets beneficiaries. Setting usually preferences assigned (Li equitable outcomes open negotiations about incurred practitioners beneficiaries involved process (Kovacs Ensuring realized successful engagement cooperation stakeholders involved. Enablers good governance, secure tenure, finance positive damages achieved implemented landholders. productivity. Yet, capital, discourage develop parallel directed incentivizing engagement, building gaining trust (Pagdee Kawasaki, Ruano-Chamorro Establishing compensatory compensating (Jack 2008). Chure previous studies found willing higher drinking they paying quality (Bhandari Incentivizing incorporation views involved, (Paudyal Wunder India, compensation protect sustainably forested return against imbalances relations rural wealthier towns created intra-community conflicts town, undermining build collective fundamental long-term existence schemes Further characterize socioeconomic status With information, direct vulnerable Li Jaramar Villarreal-Rosas conceptualization, methodology, software, validation, formal investigation, resources, writing—original draft visualization. Jonathan R. Rhodes writing—review editing supervision. Laura J. Sonter Hugh P. Possingham Adrian L. Vogl editing. All authors contributed critically drafts gave final approval publication. J.V.-R. supported University Queensland Research Training Scholarship, AOU Top Up scholarship Mexican National Council Science Technology. L.J.S. ARC Discovery Early Career Researcher Award (DE170100684). H.P.P. partially Laureate Fellowship (FL130100090). J.R.R. Future (FT200100096). confirm no conflict repository name ‘Valuing Infrastructure: Case Study (English). Washington, D.C., Group. http://documents.worldbank.org/curated/en/422301574090916059/Case-Study-of-Kali-Gandaki-Watershed-Nepal’. Land use-based stock S2. Baseline USLE C (crop) factors modelling. S3. P (practice) S4. activities. S5. Overview maps. Both axes' percentages $40M budget. Associated maps indicate unit. graphs (ha). A: map graph B: Please note: publisher responsible content functionality any supplied authors. Any queries (other missing content) should corresponding author article.