1 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia. Electronic address: kyle.morrison@unsw.edu.au.
2 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia; Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia. Electronic address: p.pottier@unsw.edu.au.
3 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia. Electronic address: pietro_pollo@hotmail.com.
4 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia. Electronic address: l.ricolfi@unsw.edu.au.
5 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia. Electronic address: coralie.williams@unsw.edu.au.
6 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia; College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, China. Electronic address: yefeng.yang1@unsw.edu.au.
7 HortSys, Univ Montpellier, CIRAD, Montpellier, France. Electronic address: beillouin@cirad.fr.
8 Laboratory of Plankton Ecology, Department of Zoology, Institute of Biology, Federal University of Juiz de Fora, Juiz de Fora 36036-900, Brazil. Electronic address: simone.jcardoso@gmail.com.
9 MARE - Marine and Environmental Sciences Centre, ARNET - Aquatic Research Network, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal. Electronic address: veronica@ci.uc.pt.
10 Department of Biology, Concordia University, Montreal, Quebec, Canada. Electronic address: brian.kenneth.gallagher@gmail.com.
11 School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom; Institute of Biology, College of Science, University of the Philippines, Diliman, Quezon City, Philippines. Electronic address: jelainegan21@gmail.com.
12 Department of Epidemiology and Statistics, School of Public Health, Guangdong Pharmaceutical University, China. Electronic address: haoguang2015@hotmail.com.
13 Social Determinants of Health Research Center, Institute for Futures Studies in Health, Kerman University of Medical Sciences, Kerman, Iran. Electronic address: mr.mojtabakeikha@gmail.com.
14 Department of Ecology and Marine Resources, Institute of Biosciences, Federal University of the State of Rio de Janeiro, Rio de Janeiro, RJ 22290-240, Brazi. Electronic address: betinaksuzuki@unirio.br.
15 ICAR-National Institute of Agricultural Economics and Policy Research (NIAP), New Delhi 110012, India. Electronic address: kiran.tm@icar.gov.in.
16 Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, Kórnik 62-035, Poland. Electronic address: latterini@man.poznan.pl.
17 Department of Ecology, University of Granada 18071 Granada, Spain; Laboratory of Ecology (iEcolab), Inter-University Institute for Earth System Research in Andalusia (IISTA), Granada, Spain. Electronic address: leverkus@ugr.es.
18 Evolution & Ecology Research Centre and the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, Australia; Charles Perkins Centre, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia. Electronic address: erin.macartney@sydney.edu.au.
19 Universidad de Alcalá, Departamento de Geología, Geografía y Medio Ambiente, A-II km 33.0, 28

Meta-analysis is commonly a core component of systematic reviews and has become an important method to reconcile conflicting findings, increase statistical power, and chart new research directions. However, poor reporting practices make it challenging to evaluate the validity of meta-analyses. Despite the existence of reporting checklists, a specifically designed tool has yet to be developed to appraise the completeness with which a meta-analysis has been reported. To bridge this gap, we introduce the Meta-analysis Appraisal Tool for Environmental Sciences (MATES). To develop MATES, we adapted a Delphi process involving experts in meta-analysis methodologies, researchers with experience in guideline/appraisal tool development, and editors of relevant journals. The Delphi process had five steps, including three workshops (11-16 participants), a survey (193 participants), and a validation task (30 participants). This iterative development process resulted in a 14-item appraisal tool that reflects the environmental science and research syntheses community's consensus on essential elements to appraise the completeness with which a meta-analysis has been reported. Validation across 50 meta-analyses demonstrated that the tool is repeatable (average agreement rate: 88.97 %) and time-efficient to implement (17.00 ± 12.23 min). We also outline guidance for interpreting MATES results, describe its potential applications, and reflect on the development process. The authors provide practical implementation guidance for each MATES item, illustrated with real examples in the supplementary material. We also report an extended development methodology to support reproducibility. Finally, we built created a ShinyApp that includes both a training module and an application tool to enhance the usability of MATES (https://kylemorrisonisshiny99.shinyapps.io/MATES_shiny/). Overall, MATES provides authors, readers, stakeholders, and editors with a reliable and accessible tool for appraising the completeness with which a meta-analysis in environmental sciences has been reported.