Open letter: The need for a site‐based biodiversity standard measuring and certifying impacts from nature‐based projects

Despite growing investment in restoration, weak accountability and poor biodiversity monitoring mean many projects fail to achieve ecological recovery. The Global Biodiversity Standard (TGBS) offers a practical way to ensure that restoration finance delivers measurable gains for nature. By providing independent, site-based verification and engaging local experts, TGBS builds trust, transparency and equity in restoration practice. Its adoption could transform how governments, investors and businesses assess success, ensuring that global restoration commitments genuinely protect, enhance and restore biodiversity. The Kunming-Montreal Global Biodiversity Framework (KM-GBF) sets out targets to halt and reverse biodiversity loss, including the ambitious aim to ensure that at least 30% of degraded ecosystems are under effective restoration by 2030. Despite ambitious pledges under the KM-GBF and other multilateral initiatives such as the Bonn Challenge, AFR100 and the Great Green Wall, large-scale restoration continues to be dominated by tree-planting schemes with widespread conflation of reforestation with restoration (Parr et al., 2024). Numerous projects have been poorly designed or have pursued other priorities, leading to unintended harm to native biodiversity from the use of monocultures, non-native and sometimes invasive species (Bond et al., 2019; Holl & Brancalion, 2020; Lewis et al., 2019). This is occurring at a time when 38% of the world's tree species are threatened with extinction (IUCN, 2024). Globally, there is a need to move biodiversity from an afterthought to a key outcome in restoration and other nature-based solutions (Brancalion et al., 2025; Seddon et al., 2021). Whilst the scale of ambition on ecosystem restoration has grown in recent years, accountability has not kept pace. Many large-scale initiatives have limited monitoring of biodiversity outcomes, creating major uncertainty about their effectiveness in recovering biodiversity and, worse still, their potential to cause collateral damage to biodiversity. Monitoring and reporting have focused heavily on planning or implementation metrics, such as hectares pledged, numbers of trees planted or tree survival rates (Gatica-Saavedra et al., 2017; Key et al., 2022). In fact, 90% of the world's largest corporations involved in restoration fail to report a single ecological outcome (Lamont et al., 2023). This lack of data and transparency leaves policymakers, businesses and investors unable to assess their impact on biodiversity, at risk of causing unintended harm and undermining the confidence that nature-based investments can generate real value. With new frameworks such as the Taskforce on Nature-related Financial Disclosures (TNFD) and the Science Based Targets for Nature (SBTN) driving greater scrutiny of corporate and financial impacts on nature, and with billions of dollars already flowing into carbon credit schemes, the absence of credible biodiversity verification represents both a material risk and a missed opportunity (Nedopil, 2023). Only through credible, site-based monitoring and independent verification of restoration outcomes can financiers avoid greenwashing, rebuild trust and provide assurance that investments are delivering measurable gains for biodiversity. Conservation and restoration practitioners, policymakers, funders, businesses, NGOs and researchers have already acknowledged the need for stronger safeguards and increased biodiversity outcomes from restoration. The Kew Declaration on reforestation for biodiversity, carbon capture and livelihoods (The Declaration Drafting Committee, 2022) was signed by over 3000 individuals and organisations from 113 countries and explicitly called for biodiversity to be placed at the centre of reforestation pledges. Meanwhile, the UNEA Resolution on Nature-based Solutions formally recognised in 2022 the necessity of biodiversity recovery in Nature-based Solutions. A set of international frameworks exists that outline best practices, including the Society for Ecological Restoration's International Principles and Standards for the Practice of Ecological Restoration (Gann et al., 2019), the UN Decade on Ecosystem Restoration Standards of Practice (Nelson et al., 2024) and, specifically for forests, the Ten Golden Rules for Reforestation (Di Sacco et al., 2021). Together, these best practice frameworks establish a strong foundation to deliver biodiversity outcomes, but until recently, a critical gap remained in translating these principles into credible, site-based verification of biodiversity outcomes. The Global Biodiversity Standard is a site-based certification scheme whose methodology builds directly on these established frameworks (Bartholomew et al., 2024). Its eight criteria are derived from the Ten Golden Rules for Reforestation (Di Sacco et al., 2021), ensuring that projects protect and enhance ecosystem integrity including biodiversity, social benefits and use of adaptive management. Changes in ecosystem integrity are assessed using the Society for Ecological Restoration (SER) Five-star System (Gann et al., 2019), applying the key concepts of project baselines and natural ecosystem reference models to measure progress over time. In addition, it builds on the UN Decade on Ecosystem Restoration Standards of Practice (Nelson et al., 2024) to assess monitoring, evaluation, and adaptive management practices. The Global Biodiversity Standard is a not-for-profit initiative, supported by a coalition of independent ecosystem restoration organisations and experts, founded and overseen by Botanic Gardens Conservation International, SER, CIFOR-ICRAF and other partners. It uses a decentralised model in which experts from biodiversity organisations such as botanical gardens are trained in The Global Biodiversity Standard methodology and deployed in their own regions. By combining the Global Biodiversity Standard's methodology with the knowledge of local biodiversity experts and Certified Ecological Restoration Practitioners (SER, 2025), The Global Biodiversity Standard ensures that site-based verification is both scientifically rigorous and grounded in local ecological and cultural knowledge. David C. Bartholomew led the initiative and wrote the first draft. Paul P. Smith, George D. Gann, Marcello De Vitis and Amarizni Mosyaftiani reviewed and edited a second version; all 258 authors have read and agreed to the final content of the letter. This article is supporting by funding from the Darwin Initiative grant DAREX001: Developing a Global Biodiversity Standard certification for tree-planting and restoration. Hadeel Ali Saeed Abdalqader, Harshavardhini Angappan, Jose A. Aranda-Pineda, Kiran Baldwin, Laura Barbosa Vedovato, Graciela M. Barreiro, David C. Bartholomew, Chris Birkinshaw, Collins Edward Bulafu, Fernanda C. G. Cardoso, Theodora Chin-Tung Chan, Mang Lung Cheuk, Tarun Chhabra, Marcello De Vitis, Dimitri D'Helft, José Manuel Fernández Zeballos, Stephan W. Gale, George D. Gann, Andrew Gichira, Orlik Gomez Garcia, Coskun Guclu, Jonathan Jenkins, David Karanja Wambui, Yogita Karpate, Alona C. Linatoc, José Manuel Mamani, Amarizni Mosyaftiani, Teresiah Mungai, Mutegeki Alislam Said Musa, Tobin Mutiso, Angie Y. S. Ng, Madhura Niphadkar, Randrianarivony Tabita Noromalalaharivelo, Alfonso Orellana-Garcia, Kato Paul, Norma Leticia Piedra Leandro, Thibaud Poulain, Sanjana Radhakrishnan, Ralainaorina Toky Niaina, Ramahefamanana Mbolasoa Narindra, Navalona Ramanambohitra, Kali Ramirez, Eliana Ramos, Michael Roy, Adriana Sandoval Comte, Ayebare Saviour, Monal Singh, Hatem Taifour, Gilles Tilman, Collins Tweheyo, Flor Gabriela Vázquez Corzas, Sebastian Walaita Javan, Wincate Wanja Kagane and Juliana Zuluaga Carrero declare that they are certified assessors of The Global Biodiversity Standard. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.