# Ongoing declines for the world's amphibians in the face of emerging threats

Jennifer Luedtke, Janice Chanson, Kelsey Neam, Louise Hobin, Adriano Maciel, Alessandro Catenazzi, Amaël Borzée, Amir Hamidy, Anchalee Aowphol, Anderson Jean, et al.

► To cite this version:

Jennifer Luedtke, Janice Chanson, Kelsey Neam, Louise Hobin, Adriano Maciel, et al. Ongoing declines for the world's amphibians in the face of emerging threats. Nature, 2023, 622 (7982), pp.308-314. 10.1038/s41586-023-06578-4. hal-05479903

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https://cnrs.hal.science/hal-05479903v1

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1

Title

2

Status of the world's amphibians: emerging threats and ongoing declines

3

Authors

Jennifer A. Luedtke¹,²*, Janice Chanson¹,², Kelsey Neam¹,², Louise Hobin², Adriano O. Maciel³,
Alessandro Catenazzi⁴,⁵, Amaël Borzée⁶,², Amir Hamidy⁷, Anchalee Aowphol⁸, Anderson Jean⁹,¹⁰,
Ángel Sosa-Bartuano¹¹, Ansel Fong G.¹², Anslem de Silva¹³, Antoine Fouquet¹⁴, Ariadne Angulo²,
Artem A. Kidov¹⁵, Arturo Muñoz Saravia¹⁶,¹⁷, Arvin C. Diesmos¹⁸,¹⁹, Atsushi Tominaga²⁰,²¹,
Biraj Shrestha²²,²³, Brian Gratwicke²⁴, Burhan Tjaturadi²⁵, Carlos C. Martínez Rivera²⁶,²⁷, Carlos
R. Vásquez Almazán²⁸,²⁹, Celsa Señaris³⁰, Chandramouli S.R.³¹, Christine Strüssmann³², Claudia
Fabiola Cortez Fernández¹⁶,³³, Claudio Azat³⁴, Conrad J. Hoskin³⁵, Craig Hilton-Taylor³⁶, Damion
L. Whyte³⁷, David J. Gower³⁸, Deanna H. Olson³⁹, Diego F. Cisneros-Heredia⁴⁰,⁴¹, Diego José
Santana⁴², Elizah Nagombi⁴³, Elnaz Najafi-Majd⁴⁴, Evan S.H. Quah⁴⁵,⁴⁶, Federico Bolaños⁴⁷,⁴⁸,
Feng Xie⁴⁹, Francisco Brusquetti⁵⁰, Francisco S. Álvarez⁵¹, Franco Andreone⁵², Frank Glaw⁵³,
Franklin Enrique Castañeda⁵⁴, Fred Kraus⁵⁵, Gabriela Parra-Olea⁵⁶, Gerardo Chaves⁴⁸, Guido F.
Medina-Rangel⁵⁷, Gustavo González-Durán⁵⁸, H. Mauricio Ortega-Andrade⁵⁹,⁶⁰, Iberê F.
Machado⁶¹, Indraneil Das⁶², Iuri Ribeiro Dias⁶³, J. Nicolas Urbina-Cardona⁶⁴, Jelka Crnobrnja-
Isailović⁶⁵, Jian-Huan Yang⁶⁶, Jiang Jianping⁴⁹, Jigme Tshelthrim Wangyal⁶⁷,⁶⁸, Jodi J.L.
Rowley⁶⁹,⁷⁰, John Measey⁷¹,⁷², Karthikeyan Vasudevan⁷³, Kin Onn Chan⁴⁶, Kotambylu Vasudeva
Gururaja⁷⁴, Kristiina Ovaska⁷⁵,⁷⁶, Lauren C. Warr⁷⁷, Luis Canseco-Márquez⁷⁸, Luís Felipe
Toledo⁷⁹, Luis M. Díaz⁸⁰, M. Monirul H. Khan⁸¹, Madhava Meegaskumbura⁸², Manuel E.
Acevedo⁸³, Marcelo Felgueiras Napoli⁸⁴, Marcos A. Ponce⁸⁵, Marcos Vaira⁸⁶, Margarita
Lampo⁸⁷,⁸⁸, Mario H. Yánez-Muñoz⁸⁹, Mark D. Scherz⁹⁰, Mark-Oliver Rödel⁹¹, Masafumi
Matsui⁹², Maxon Fildor⁹, Mirza D. Kusrini⁹³, Mohammad Firoz Ahmed⁹⁴, Muhammad Rais⁹⁵,
N'Goran G. Kouamé⁹⁶, Nieves García⁹⁷, Nono Legrand Gonwouo⁹⁸, Patricia A. Burrowes⁹⁹, Paul
Y. Imbun¹⁰⁰, Philipp Wagner¹⁰¹,¹⁰², Philippe J. R. Kok¹⁰³,¹⁰⁴, Rafael L. Joglar¹⁰⁵,¹⁰⁶, Renoir J.
Auguste¹⁰⁷, Reuber Albuquerque Brandão¹⁰⁸, Roberto Ibáñez¹⁰⁹, Rudolf von May¹¹⁰, S. Blair
Hedges¹¹¹, S.D. Biju¹¹², S.R. Ganesh¹¹³, Sally Wren²,¹¹⁴, Sandeep Das¹¹⁵,¹¹⁶, Sandra V. Flechas¹¹⁷,
Sara L. Ashpole¹¹⁸,¹¹⁹, Silvia J. Robleto-Hernández¹²⁰, Simon P. Loader³⁸, Sixto J. Incháustegui¹²¹,
Sonali Garg¹²²,¹¹², Soumphthone Phimmachak¹²³, Stephen J. Richards¹²⁴, Tahar Slimani¹²⁵,
Tamara Osborne-Naikatini¹²⁶, Tatianne P. F. Abreu-Jardim⁶¹, Thais H. Condez¹²⁷, Thiago R. De
Carvalho¹²⁸, Timothy P. Cutajar⁶⁹,¹²⁹, Todd W. Pierson¹³⁰, Truong Q. Nguyen¹³¹, Uğur Kaya⁴⁴,
Zhiyong Yuan¹³², Barney Long¹, Penny Langhammer¹,¹³³, Simon N. Stuart⁹⁷,¹³⁴,¹³⁵

33

Affiliations

34

¹Re: wild; Austin, Texas, USA.

35

²IUCN SSC Amphibian Specialist Group; Toronto, Ontario, Canada.
36 ³Museu Paraense Emílio Goeldi, CZO/Herpetologia; Belém, Pará, Brazil.

37 ⁴Florida International University; Miami, Florida, USA.

38 ⁵Centro de Ornitologia y Biodiversidad (CORBIDI); Surco, Lima, Peru.

39 ⁶Laboratory of Animal Behaviour and Conservation, College of Biology and the Environment, Nanjing Forestry University; Nanjing, People's Republic of China.

41 ⁷Laboratory of Herpetology, Museum Zoologicum Bogoriense, Research Center for Biosystematics and Evolution, National Research and Innovation Agency (BRIN); Cibinong, Indonesia.

44 ⁸Department of Zoology, Faculty of Science, Kasetsart University; Bangkok, Thailand.

45 ⁹Action Pour la Sauvegarde de l'Ecologie en Haïti (ACSEH); Les Cayes, Haiti.

46 ¹⁰Environmental Protection In the Caribbean (EPIC); Maho, Sint Maarten, Dutch West Indies.

47 ¹¹Museo de Vertebrados de la Universidad de Panamá; Ciudad de Panamá, Panamá.

48 ¹²Centro Oriental de Ecosistemas y Biodiversidad (BIOECO), Museo de Historia Natural “Tomás Romay”; Santiago de Cuba, Cuba.

50 ¹³IUCN SSC Amphibian Specialist Group, Sri Lanka; Gampola, Sri Lanka.

51 ¹⁴Laboratoire Évolution & Diversité Biologique, UMR 5174, Université Toulouse III Paul Sabatier; Toulouse, France.

53 ¹⁵Russian State Agrarian University – MTAA; Moscow, Russia.

54 ¹⁶IUCN SSC Amphibian Specialist Group Bolivia; La Paz, Bolivia.

55 ¹⁷Animal Nutrition Unit, Department of Veterinary and Biosciences, Ghent University; Ghent, Belgium.

57 ¹⁸ASEAN Centre for Biodiversity, University of the Philippines Los Baños; Laguna, Philippines.

58 ¹⁹HerpWatch Pilipinas, Inc.; Tondo, Manila, Philippines.

59 ²⁰Faculty of Education, University of the Ryukyus; Okinawa, Japan.

60 ²¹Graduate School of Engineering and Science, University of the Ryukyus; Okinawa, Japan.

61 ²²SAVE THE FROGS!; Laguna Beach, California, USA.

62 ²³The University of Texas at Arlington; Arlington, Texas, USA.

63 ²⁴Smithsonian Conservation Biology Institute; Front Royal, Virginia, USA.

64 ²⁵Center for Environmental Studies, Sanata Dharma University (CESSDU); Yogyakarta, Indonesia

66 ²⁶Pinelands Preservation Alliance; Southampton Township, New Jersey, USA.

67 ²⁷Centro de Conservación de Anfibios, Amaru Bioparque; Cuenca, Ecuador.

68 ²⁸Museo de Historia Natural, Escuela de Biologia, Universidad de San Carlos; Guatemala City, Guatemala.

70 ²⁹FUNDAECO; Guatemala City, Guatemala.

71 ³⁰Estación Biológica de Doñana (EBD-CSIC); Sevilla, Spain.

72 ³¹Department of Ecology and Environmental Sciences, Pondicherry University; Puducherry, India.

74 ³²Universidade Federal de Mato Grosso; Cuiabá, Mato Grosso, Brazil.

75 ³³Museo Nacional de Historia Natural; La Paz, Bolivia.
76 ³⁴Sustainability Research Center & PhD Program in Conservation Medicine, Faculty of Life Sciences, Universidad Andres Bello; Republica, Santiago, Chile.

77

78 ³⁵College of Science & Engineering, James Cook University; Townsville, Queensland, Australia.

79 ³⁶IUCN, David Attenborough Building; Cambridge, United Kingdom.

80 ³⁷Department Of Life Sciences, University of the West Indies Mona; Kingston, Jamaica.

81 ³⁸The Natural History Museum; London, United Kingdom.

82 ³⁹United States Department of Agriculture, Forest Service, Pacific Northwest Research Station;

83 Corvallis, Oregon, USA.

84 ⁴⁰Universidad San Francisco de Quito USFQ, Colegio de Ciencias Biológicas y Ambientales,

85 Instituto de Biodiversidad Tropical IBIOTROP; Quito, Ecuador.

86 ⁴¹Instituto Nacional de Biodiversidad INABIO; Quito, Ecuador.

87 ⁴²Instituto de Biociências, Universidade Federal de Mato Grosso do Sul; Campo Grande, Mato

88 Grosso do Sul, Brazil.

89 ⁴³The New Guinea Binatang Research Center; Nagada Harbour, Madang, Papua New Guinea.

90 ⁴⁴Department of Zoology, Faculty of Science, Ege University; Bornova, İzmir, Turkey.

91 ⁴⁵Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah; Kota Kinabalu,

92 Sabah, Malaysia.

93 ⁴⁶Lee Kong Chian Natural History Museum, National University of Singapore; Singapore,

94 Singapore.

95 ⁴⁷Escuela de Biología, Universidad de Costa Rica; San Pedro, San José, Costa Rica.

96 ⁴⁸CIBET (Museo de Zoología), Universidad de Costa Rica; San Pedro, San José, Costa Rica.

97 ⁴⁹Chengdu Institute of Biology, Chinese Academy of Sciences; Chengdu, People's Republic of

98 China.

99 ⁵⁰Instituto de Investigación Biológica del Paraguay; Asunción, Paraguay.

100 ⁵¹Fundación Naturaleza El Salvador; Colonia Escalón, San Salvador, El Salvador.

101 ⁵²Museo Regionale di Scienze Naturali; Torino, Italy.

102 ⁵³Zoologische Staatssammlung München (ZSM-SNSB); München, Germany.

103 ⁵⁴Panthera; Tegucigalpa, Honduras.

104 ⁵⁵Department of Ecology and Evolutionary Biology, University of Michigan; Ann Arbor,

105 Michigan, USA.

106 ⁵⁶Instituto de Biologia, Universidad Nacional Autónoma de México; Ciudad de México, CDMX,

107 Mexico.

108 ⁵⁷Instituto de Ciencias Naturales, Universidad Nacional de Colombia; Bogotá D.C., Colombia.

109 ⁵⁸WCS-Colombia; Cali, Valle del Cauca, Colombia.

110 ⁵⁹Biogeography and Spatial Ecology Research Group, Life Sciences Faculty, Universidad

111 Regional Amazónica IKIAM; Tena, Ecuador.

112 ⁶⁰Herpetology Division, Instituto Nacional de Biodiversidad; Quito, Pichincha, Ecuador.

113 ⁶¹Instituto Boitatá de Etnobiologia e Conservação da Fauna, Goiânia, Goiás, Brazil.

114 ⁶²Institute of Biodiversity and Environmental Conservation, Universiti Malaysia Sarawak; Kota

115 Samarahan, Sarawak, Malaysia.
116 ⁶³Universidade Estadual de Santa Cruz, Departamento de Ciências Biológicas; Ilhéus, Bahia,
117 Brazil.
118 ⁶⁴Pontificia Universidad Javeriana, Facultad de Estudios Ambientales y Rurales, Departamento
de Ecología y Territorio; Bogotá, Colombia.

120 ⁶⁵University of Niš Faculty of Sciences and Mathematics Department of Biology and Ecology;
121 Niš, Serbia.

122 ⁶⁶Kadoorie Farm and Botanic Garden; Tai Po, Hong Kong SAR, People's Republic of China.

123 ⁶⁷University of New England; Armidale, NSW, Australia.

124 ⁶⁸Bhutan Ecological Society; Thimphu, Bhutan.

125 ⁶⁹Australian Museum Research Institute, Australian Museum; Sydney New South Wales,
126 Australia.

127 ⁷⁰Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences
128 (BEES), University of New South Wales; Sydney, New South Wales, Australia.

129 ⁷¹Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University;
130 Stellenbosch, South Africa.

131 ⁷²Centre for Invasion Biology, Institute of Biodiversity, School of Ecology and Environmental
132 Science, Yunnan University; Kunming, People's Republic of China.

133 ⁷³CSIR-Centre for Cellular and Molecular Biology, Laboratory for the Conservation of
134 Endangered Species; Hyderabad, India.

135 ⁷⁴Srishti Manipal Institute of Art, Design and Technology, Manipal Academy of Higher
136 Education; Manipal, India.

137 ⁷⁵Biolinx Environmental Research Ltd.; Victoria, British Columbia, Canada.

138 ⁷⁶Royal British Columbia Museum; Victoria, British Columbia, Canada.

139 ⁷⁷Flint, Texas, USA.

140 ⁷⁸Laboratorio de Herpetología, Facultad de Ciencias, Universidad Nacional Autónoma de
141 México; Ciudad de México, CDMX, Mexico.

142 ⁷⁹Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Universidade Estadual de
143 Campinas (Unicamp); Campinas, São Paulo, Brazil.

144 ⁸⁰Museo Nacional de Historia Natural de Cuba; La Habana, Cuba.

145 ⁸¹Department of Zoology, Jahangirnagar University, Savar, Dhaka, Bangladesh.

146 ⁸²Key Laboratory in Forest Ecology and Conservation, College of Forestry, Guangxi University;
147 Nanning, People's Republic of China.

148 ⁸³Museo Nacional de Historia Natural "Jorge A. Ibarra"; Ciudad de Guatemala, Guatemala.

149 ⁸⁴Instituto de Biologia, Campus Universitário de Ondina, Universidade Federal da Bahia;
150 Salvador, Bahia, Brazil.

151 ⁸⁵David, Provincia de Chiriquí, Panamá.

152 ⁸⁶Instituto de Ecorregiones Andinas (INECOA, UNJu - Conicet); San Salvador de Jujuy, Jujuy,
153 Argentina.

154 ⁸⁷Instituto Venezolano de Investigaciones Científicas (IVIC); Miranda, Venezuela.
¹⁵⁵ ⁸⁸Fundación para el Desarrollo de las Ciencias Físicas, Matemáticas y Naturales (FUDECI);
Caracas, Venezuela.

¹⁵⁷ ⁸⁹Unidad de Investigación, Instituto Nacional de Biodiversidad (INABIO); Quito, Ecuador.

¹⁵⁸ ⁹⁰Natural History Museum of Denmark, University of Copenhagen; Copenhagen, Denmark.

¹⁵⁹ ⁹¹Museum für Naturkunde - Leibniz Institute for Evolution and Biodiversity Science; Berlin,
Germany.

¹⁶¹ ⁹²Kyoto University, Yoshida Nihonmatsu; Sakyoku, Kyoto, Japan.

¹⁶² ⁹³Faculty of Forestry & Environment, IPB University; Bogor, Indonesia.

¹⁶³ ⁹⁴Aaranyak; Beltola, Guwahati, Assam, India.

¹⁶⁴ ⁹⁵Herpetology Lab, Department of Zoology, Wildlife and Fisheries, Pir Mehr Ali Shah Arid
Agriculture University Rawalpindi; Rawalpindi, Pakistan.

¹⁶⁶ ⁹⁶Laboratoire de Biodiversité et Ecologie Tropicale, UFR Environnement, Université Jean
Lorougnon Guédé; Daloa, Côte d'Ivoire.

¹⁶⁸ ⁹⁷IUCN Species Survival Commission; Gland, Switzerland.

¹⁶⁹ ⁹⁸University of Yaoundé I, Faculty of Science Laboratory of Zoology; Yaoundé, Cameroon.

¹⁷⁰ ⁹⁹University of Puerto Rico, Department of Biology; San Juan, Puerto Rico.

¹⁷¹ ¹⁰⁰Sabah Parks, Research and Education Section, Zoology Unit; Kota Kinabalu, Sabah, Malaysia.

¹⁷² ¹⁰¹Allwetterzoo; Münster, Germany.

¹⁷³ ¹⁰²Villanova University, Center for Biodiversity and Ecosystem; Villanova, Pennsylvania, USA.

¹⁷⁴ ¹⁰³Department of Ecology and Vertebrate Zoology, Faculty of Biology and Environmental
Protection, University of Łódź; Łódź, Poland.

¹⁷⁶ ¹⁰⁴Department of Life Sciences, The Natural History Museum; London, United Kingdom.

¹⁷⁷ ¹⁰⁵University of Puerto Rico - Rio Piedras Campus; San Juan, Puerto Rico.

¹⁷⁸ ¹⁰⁶Proyecto Coqui; San Juan, Puerto Rico.

¹⁷⁹ ¹⁰⁷Department of Life Sciences, The University of the West Indies; St. Augustine, Trinidad and
Tobago.

¹⁸¹ ¹⁰⁸Laboratório de Fauna e Unidades de Conservação, Universidade de Brasília; Brasília-DF,
Brazil.

¹⁸³ ¹⁰⁹Smithsonian Tropical Research Institute; Panamá, República de Panamá.

¹⁸⁴ ¹¹⁰California State University Channel Islands; Camarillo, California, USA.

¹⁸⁵ ¹¹¹Center for Biodiversity, Temple University; Philadelphia, Pennsylvania, USA.

¹⁸⁶ ¹¹²Systematics Lab, Department of Environmental Studies, University of Delhi; Delhi, India.

¹⁸⁷ ¹¹³Chennai Snake Park; Chennai, Tamil Nadu, India.

¹⁸⁸ ¹¹⁴Department of Zoology, University of Otago; Dunedin, New Zealand.

¹⁸⁹ ¹¹⁵Department of Zoology, St. Joseph's College (Autonomous); Thrissur, Kerala, India.

¹⁹⁰ ¹¹⁶EDGE of Existence programme, Conservation and Policy, Zoological Society of London;
London, United Kingdom.

¹⁹² ¹¹⁷Bichos.team; Bogotá, Colombia.

¹⁹³ ¹¹⁸Environmental Studies, St. Lawrence University; Canton, New York, USA.

¹⁹⁴ ¹¹⁹Prescott, Ontario, Canada.
195 <sup>120</sup>IUCN SSC Amphibian Specialist Group Nicaragua; Managua, Nicaragua.

196 <sup>121</sup>Grupo Jaragua; Santo Domingo, Dominican Republic.

197 <sup>122</sup>Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, 198 Harvard University; Cambridge, Massachusetts, USA.

199 <sup>123</sup>National University of Laos, Faculty of Natural Sciences, Department of Biology; Vientiane, 200 Laos.

201 <sup>124</sup>Herpetology Department, South Australian Museum; Adelaide, South Australia, Australia.

202 <sup>125</sup>Faculty of Sciences Sremlalia, Cadi Ayyad University; Marrakech, Morocco.

203 <sup>126</sup>School of Agriculture, Geography, Environment, Ocean and Natural Sciences, The University 204 of the South Pacific; Suva, Fiji.

205 <sup>127</sup>Carleton University, Department of Earth Sciences; Ottawa, Ontario, Canada.

206 <sup>128</sup>Universidade Federal de Minas Gerais; Belo Horizonte, Minas Gerais, Brazil.

207 <sup>129</sup>Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences 208 (BEES), University of New South Wales; Sydney, New South Wales, Australia.

209 <sup>130</sup>Department of Ecology, Evolution, and Organismal Biology, Kennesaw State University; 210 Kennesaw, Georgia, USA.

211 <sup>131</sup>Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology; 212 Ha Noi, Viet Nam.

213 <sup>132</sup>School of Life Sciences, Southwest University; Chongqing, People's Republic of China.

214 <sup>133</sup>Arizona State University; Tempe, Arizona, USA.

215 <sup>134</sup>A Rocha International; London, United Kingdom.

216 <sup>135</sup>Synchronicity Earth; London, United Kingdom.

217 *Corresponding author. Email: jluedtke@rewild.org

218 **Abstract**

219 Systematic assessments of species extinction risk at regular intervals are necessary for informing 220 conservation action. Ongoing developments in taxonomy, threatening processes, and research 221 further underscore the need for reassessment. The second Global Amphibian Assessment evaluates 222 8,011 species for the IUCN Red List and finds amphibians are the most threatened vertebrate class 223 (40.7%). The updated Red List Index shows their status is deteriorating globally, particularly for 224 salamanders and the Neotropics. Disease and habitat loss drove 91% of status deteriorations 225 between 1980–2004. Ongoing and projected climate change effects are now of increasing concern, 226 driving 39% of status deteriorations since 2004, followed by habitat loss (37%). While signs of
species recoveries incentivize immediate conservation action, scaled-up investment is urgently needed to reverse current trends.

## Summary Paragraph

The IUCN Red List Index documents the extinction risk trends of species groups over time¹, generating information crucial for conservation prioritisation and planning². The second Global Amphibian Assessment comprehensively assesses the extinction risk of amphibians for the first time since the 2004 baseline³. This study 1) identifies species with the highest current extinction risk and those deteriorating towards extinction at the highest rate, 2) focuses conservation efforts onto the most pressing issues, and 3) evaluates the effectiveness of these efforts. It shows the number of threatened and extinct species is increasing, confirming amphibians as the most threatened vertebrate class. Extinction risk is highest in the Neotropical realm and in salamander families. While habitat loss affects the majority of threatened amphibians, disease is driving them to extinction faster, and climate change is emerging as a major driver of increases in extinction risk. The results also demonstrate that habitat protection is effective in reducing extinction risk but has been insufficient in scale. For species threatened by over-exploitation, climate change, or disease, additional measures are urgently needed. Avoiding further declines and halting amphibian extinctions require a substantial increase in investment and stronger political will for conservation goals.

## Main

The landmark 2004 Global Amphibian Assessment (GAA1) demonstrated that amphibians were the most threatened class of vertebrates worldwide and has been widely used to guide and motivate amphibian conservation efforts³. This baseline study identified habitat loss and degradation and
over-exploitation as the main threats contributing to just over half of the species that deteriorated in status between 1980–2004, while 48% were classified as “enigmatic-decline species”³.

Subsequent studies support that the disease chytridiomycosis, caused by *Batrachochytrium dendrobatidis* (*Bd*), was most likely responsible for many enigmatic declines⁴,⁵,⁶,⁷,⁸. The GAA1 helped launch a wave of research and conservation efforts directed at *Bd* and the other threats causing the decline of amphibians².

Completed in June 2022, the second Global Amphibian Assessment (GAA2) reassessed the status of the GAA1 species and added 2,286 species, bringing the number of amphibians on the IUCN Red List of Threatened Species™ (hereafter Red List) to 8,011 (39.9% increase from 2004; covering 92.9% of 8,615 described species). Since the GAA1, information on population trends, ecological requirements, threats, and distributional boundaries of amphibians has improved considerably, and amphibian systematics have progressed. However, this new information (e.g., better estimates of population size, redefining taxonomic boundaries) can sometimes result in a non-genuine change in Red List category, introducing biases in the data. Therefore, we use current information to estimate a backcasted Red List category for each species in 1980 and 2004 and examine only genuine category changes. With these data and the GAA2 assessments, we reexamine the global status and trends of amphibians and present new insights on threats, providing a crucial update which informs the prioritisation, planning, and monitoring of conservation actions.

## **Threatened and extinct species**

The status of amphibians worldwide continues to deteriorate: 40.7% (2,873) are globally threatened (i.e., Red List categories Critically Endangered, Endangered, and Vulnerable),
compared to 37.9% (2,681) in 1980 and 39.4% (2,788) in 2004 (Fig. 1, Methods 4.1, Extended Data Table 1). The proportion of Data Deficient (DD) species has decreased from 22.5% in the GAA1 to 11.3% as a result of newly available information.

The greatest concentrations of threatened species are in the Caribbean islands, Mesoamerica, the Tropical Andes, the mountains and forests of western Cameroon and eastern Nigeria, Madagascar, the Western Ghats, and Sri Lanka. Other significant concentrations of threatened species occur in the Atlantic Forest biome of southern Brazil, the Eastern Arc Mountains of Tanzania, central and southern China, and the southern Annamite Mountains of Viet Nam (Fig. 1). Of all comprehensively assessed groups on the IUCN Red List, amphibians are the second most threatened group and remain the most threatened vertebrate class (cycads, 69%; sharks and rays, 37.4%; conifers, 34.0%; reef-building corals, 33.4%; mammals, 26.5%; reptiles, 21.4%; dragonflies, 16%; birds, 12.9%; cone snails, 6.5%)[9,10,11,12,13,14,15].

Documented amphibian extinctions continue to increase: there were 23 by 1980, an additional 10 by 2004, and four more by 2022, for a total of 37 (Extended Data Table 1). The most recent are *Atelopus chiriquiensis* and *Taudactylus acutirostris*, after rapid declines linked to chytridiomycosis in the 1990s, while *Craugastor myllomyllon* and *Pseudoeurycea exspectata* were last seen in the 1970s and believed Extinct because of agricultural expansion. Strict requirements must be met to declare a species Extinct¹⁶; therefore, many species missing for decades are categorised as Critically Endangered (CR) and tagged as “Possibly Extinct” (PE). In 1980, 24 amphibians were CR(PE), by 2004 this increased to 162, with another 23 added by 2022 (Extended Data Table 1). Thus, the number of known amphibian extinctions could be as many as 223 over the last 150 years, if all CR(PE) species are indeed extinct.
293 When considering all threatened amphibians, the most commonly documented threats are types of 294 habitat loss and degradation, with the top three being agriculture (77% of species impacted), timber 295 and plant harvesting (53%), and infrastructure development (40%) (Fig. 2, Extended Data Table 296 2). Climate change effects (25%) and disease (20%) are other common threat types. While these 297 are important findings, they do not account for the severity and scope of these threats.

298 **Red List Index (RLI)**

299 The Red List Index (RLI) is an indicator calculated from Red List categories to measure trends in 300 extinction risk over time¹. RLI values range from 1 (all species are Least Concern) to 0 (all are 301 Extinct). A change in value is influenced only by species moving between categories due to 302 genuine improvements or deteriorations in status, with non-genuine category changes excluded 303 through backcasting (Methods Section 4.3). The RLI is calculated for amphibians for 1980, 2004, 304 and 2022 using the data collected in this study, and compared to other species groups⁹ (Fig. 3a). A 305 negative RLI trend is observed in all groups with more than one RLI data point, indicating that the 306 number of species in higher extinction risk categories is increasing (Fig. 3a). While the amphibian 307 RLI trend between 2004–2022 is slightly less steep compared to the previous period, it continues 308 to decline.

309 Trends in extinction risk differ across biogeographic realms (Fig. 3b, Extended Data Table 3). The 310 Neotropics (with 48% of amphibians) has the lowest RLI value of all realms and the greatest 311 deterioration in status, although the gradient lessens during 2004–2022. The Neotropical trend is 312 associated with chytridiomycosis outbreaks in the 1970s–2000s, with many of the most susceptible 313 species affected pre-2004. Australasia has the highest RLI, primarily because there are 314 comparatively fewer threats to the large number of species on New Guinea, currently a
chytridiomycosis free refuge¹⁷ with a reasonable possibility of a period of outbreak and decline in the future. The Palearctic and Nearctic RLIs show accelerating declines during 2004–2022. In the Palearctic, habitat loss/degradation is the leading cause followed by the emerging threat of the fungal pathogen, *Batrachochytrium salamandrivorans* (Bsal), whereas in the Nearctic, climate change effects are the most common cause, followed by habitat loss/degradation. The RLI trend for the Afrotropics is declining across both periods, initially driven by habitat loss/degradation, but more recently disease emerges as the most common cause. The Indomalayan RLI trend shows a slight improvement between 2004–2022, likely owing to the creation and improved management of protected areas.

Among the three most common breeding strategies for amphibians, extinction risk is higher for direct developers than larval developers and live bearers (Methods Section 2.3, Fig. 3c, Extended Data Table 3). The RLI of all three groups declined at a similar rate between 1980–2004. During 2004–2022, however, it slows for larval developers and slightly accelerates for live bearers and direct developers. This result is likely due to larval developers having been especially impacted by Bd prior to 2004 when chytridiomycosis outbreaks were at their peak (particularly in high-elevation streams). The causes of differing extinction risks between breeding strategies merit further study.

Extinction risk also exhibits important phylogenetic patterns (Fig. 3d, Extended Data Table 3). The RLI for Caudata (salamanders and newts) is consistently the lowest, making them the most threatened. Although the RLI for Caudata declined at a lesser rate than for Anura (frogs) during 1980–2004, the rate of decline increased between 2004–2022. In contrast, the RLI for Anura declined at a much greater rate between 1980–2004, but at a lesser rate between 2004–2022, likely due to the timing of global chytridiomycosis outbreaks. A slight downward trend is shown for
338 Gymnophiona (caecilians) with the caveat that they are very poorly studied: only 115 of the 206
339 assessed are included in the RLI due to 44% being categorised as DD, and 17% are threatened.

340 Genuine Changes in Status

341 To better understand which threats are driving deteriorations in status, the subset of species that
342 changed Red List categories over time are examined further. For each species in the subset, the
343 threat that contributed most substantially to the deterioration in status is determined and defined
344 as the “primary driver”. These are categorised into four main groups: disease, climate change
345 effects, habitat loss/degradation, and over-exploitation (Methods Section 4.4, Extended Data Table
346 2). Since 1980, 87% of category changes were into a higher extinction risk category, with 482 of
347 those changes occurring between 1980–2004 and 306 between 2004–2022 (Supplementary
348 Information Data 1).

349 The geographic pattern of primary drivers for amphibians with a deteriorating status is not uniform
350 (Fig. 4). Disease is the primary driver for 281 species (58%) during 1980–2004, compared to 69
351 species (23%) during 2004–2022 (Extended Data Table 2). It is recorded as the dominant primary
352 driver of status deteriorations from Costa Rica to the Andes of South America during 1980–2004
353 and 2004–2022, while newer hotspots of disease-related declines are appearing in central and
354 eastern Africa (Fig. 4). *Bsal* is an emerging threat in Europe (Fig. 4b), where status deteriorations
355 are being driven by projected declines for some species.

356 There are some interesting points of difference when comparing the current distribution map of all
357 threatened species (Fig. 1) to the distribution of species that have deteriorated in status between
358 2004–2022 (Fig. 4b). Several global hotspots for threatened amphibians such as Madagascar,
359 Hispaniola, the Eastern Arc Mountains of Tanzania, and the southern Annamite Mountains of Viet
Nam are notably absent from the map of species that deteriorated in status. In these regions threats have been ongoing for decades, and many species are already considered highly threatened. For example, deteriorations in status due to disease and high rates of habitat loss on Hispaniola are apparent in the previous time period 1980–2004 (Fig. 4a), with a large proportion of species endemic to the island already on the brink of extinction at the time GAA1 was completed. On the contrary, other global hotspots for threatened amphibians continue to experience status deteriorations. Two of the most speciose regions of the world for amphibians, the Tropical Andes and Mesoamerica, have held considerable numbers of species that have deteriorated in status since 1980.

Species moving into the highest extinction risk categories are much more likely to have been affected by disease (Fig. 5), as chytridiomycosis results in rapid and widespread population declines for susceptible species⁵,⁶. Disease is the primary driver for 76% of category changes to CR and 79% of changes to CR(PE) between 1980–2004 and remains the primary driver pushing species into CR(PE) between 2004–2022 (89%; Fig. 5). In contrast, status deteriorations due to projected climate change effects are more frequently into categories of lower extinction risk (i.e., Near Threatened or Vulnerable).

Climate change effects are the most common primary driver of status deteriorations during 2004–2022, with 119 species (39%) compared to six species (1%) during 1980–2004 (Fig. 4, Extended Data Table 2). A noteworthy example is the amphibians endemic to Venezuelan tepuis (table-top mountains) (Fig. 4b, Supplementary Table 1), which are particularly vulnerable to predicted habitat shifting due to climate change because vertical migration and dispersal are impossible.

Decreased rainfall due to climate change in the Wet Tropics of Australia and Brazil's Atlantic Forest is also predicted to reduce the reproductive success of direct-developing frogs (e.g., in the
genera *Cophixalus* and *Brachycephalus*) because of their dependence on high levels of soil and
leaf-litter moisture to prevent egg desiccation. In eastern Australia and western United States,
climate change is increasing the frequency, duration, and severity of droughts and fires¹⁸, often
compounding existing threats from disease and habitat loss. For example, five US salamander
species in the genus *Batrachoseps* have deteriorated in status due to the increasing effects of fires
and reduced soil humidity. Given the scarcity and geographic bias of studies on the effects of
climate change on amphibians¹⁹, the true impacts are likely underestimated. As further studies are
published and climate change effects continue to increase and intensify, the status of additional
amphibians is expected to deteriorate.

Habitat loss/degradation remains the most prevalent primary driver of status deteriorations in many
regions (156 species or 32% in 1980–2004, 112 species or 37% in 2004–2022) (Extended Data
Table 2). Between 2004–2022, hotspots caused by ongoing or projected habitat loss are prominent
in the Andes of Ecuador, central Guyana, and Republic of Korea (Fig. 4b).

While most category changes since 1980 are deteriorations (788), 120 species have shown
improvements in status, moving to less threatened Red List categories (Extended Data Fig. 1,
Supplementary Information Data 2). Conservation actions are responsible for 63 of these
improvements, 94% of which are results from effective habitat protection and improved habitat
management in regions such as the Western Ghats in India, Costa Rica, and Sabah in Malaysia.

Another 57 species (largely from the Neotropics and Australia) improved unaided, most of which
are now persisting, and in some cases recovering, after experiencing a rapid decline associated
with chytridiomycosis. It is evident that there are still no definitive conservation measures known
to prevent ongoing decline from disease in wild populations, although many of these species can
benefit from habitat protection. For example, some species that previously experienced declines
due to disease, but are now persisting, have improved in status because their habitat has remained
protected (e.g., Australian species: *Litoria aurea*, *L. dayi*, *L. nannotis*, *L. pearsoniana*, *L. raniformis*, and *L. rheocola*). Whereas other species that are persisting post-Bd declines may not
experience an improvement in category if high rates of habitat loss and degradation are present
within their distributions.

## Discussion

The findings of this study confirm that the global amphibian extinction crisis has not abated.
Crucially, the primary driver of status deteriorations is shifting from disease to the emerging threat
of climate change. This is of particular concern because it often exacerbates other threats, such as
land-use change, fire, or disease<sup>20,21,22</sup>. Therefore, the GAA2 results highlight the need to
investigate and implement conservation actions that address the species-specific effects of climate
change, particularly for species identified as imminently at risk of serious population declines.

This study also reinforces that effective habitat protection continues to be a priority for amphibian
conservation, as it contributed to the greatest number of status improvements since 1980. However,
more amphibians are threatened with extinction than ever before, underscoring the urgency of
halting the destruction and degradation of their habitats. Critically, the legal and illegal expansion
of agriculture, including animal agriculture and cash crops, is the single most important threat to
amphibians worldwide (Fig. 2). Effective protection of globally important sites for amphibians,
including Alliance for Zero Extinction sites and other Key Biodiversity Areas<sup>23</sup> (two conservation
tools that draw on IUCN Red List data), can safeguard remaining habitat for threatened or
geographically restricted species.
The GAA2 data also demonstrate that effective habitat protection alone is not always sufficient in addressing the threats of disease, over-exploitation, or climate change effects, as many threatened amphibians already occur within protected areas. Thus, the integration of priority amphibian sites within the wider landscape, to ensure connectivity and enable dispersal, will be important in the face of global change scenarios, as has also been suggested by other studies²⁴,²⁵. Furthermore, to avoid a second global amphibian pandemic, which has the potential to trigger a new wave of status deteriorations similar to those related to Bd (Fig. 4a, Fig. 5a), preventing the spread of Bsal throughout Europe and its introduction into the Americas is essential²⁶,²⁷,²⁸. Monitoring populations for other novel disease risks²⁹ and developing practical disease management tools are also recommended. Integrating ex-situ measures into conservation plans can buy time³⁰, especially for the 797 CR species that are at highest risk of extinction.

The large proportion of DD amphibians (909 species) continue to require further research to determine their extinction risk and conservation needs (Methods Section 3.3). Many of these are likely to be threatened³¹,³²,³³. More broadly, increased population monitoring worldwide³⁴ is crucial to informing conservation actions and future reassessments. These with other recommended actions are highlighted in the IUCN SSC Amphibian Conservation Action Plan³⁵.

In support of the conservation actions above, policy responses to the ongoing amphibian extinction crisis, and the biodiversity crisis as a whole, need to be strengthened. Increased political will and sufficient resource commitments for the delivery of agreed global and national biodiversity conservation targets are necessary for the future survival and recovery of this amazingly diverse group of animals.
448 **Main References**

449 1. Butchart, S. H. M. et al. Improvements to the Red List Index. *PLoS One* **2**, e140 (2007).

450 2. IUCN/SSC Amphibian Specialist Group. *Amphibian Conservation Action Plan* (eds. Gascon, C. et al.) (Cambridge, UK and Gland, Switzerland: IUCN, 2007).

452 3. Stuart, S. N. et al. Status and trends of amphibian declines and extinctions worldwide. *Science* **306**, 1783–1786 (2004).

454 4. Lips, K. R., Diffendorfer, J., Mendelson, J. R. III & Sears, M. W. Riding the wave: Reconciling the roles of disease and climate change in amphibian declines. *PLOS Biol.* **6**, e72 (2008).

457 5. Skerratt, L. F. et al. Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. *EcoHealth* **4**, 125–134 (2007).

459 6. Lips, K. R. Overview of chytrid emergence and impacts on amphibians. *Phil. Trans. R. Soc. B* **371**, 20150465 (2016).

461 7. O'Hanlon, S. J. et al. Recent Asian origin of chytrid fungi causing global amphibian declines. *Science* **360**, 621–627 (2018).

463 8. Scheele, B.C. et al. Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity. *Science* **363**, 1459–1463 (2019).

465 9. IUCN. *The IUCN Red List of Threatened Species* v.2022-1 https://www.iucnredlist.org (2022).

467 10. Hills, R. et al. Raising awareness through the Global Tree Assessment: Extinction risk of six fully assessed tree groups. *Plants, People, Planet*, 1–11 (2022).

469 11. Carpenter, K. E. et al. One-third of reef-building corals face elevated extinction risk from climate change and local impacts. *Science* **321**, 560–563 (2008).
471 12. Hoffmann, M. et al. The changing fate of the world's mammals. Phil. Trans. R. Soc. B 366, 2598-2610 (2011).

473 13. Cox, N. et al. A global reptile assessment highlights shared conservation needs of tetrapods. Nature 605, 285-290 (2022).

475 14. BirdLife International. State of the world's birds: taking the pulse of the planet (Cambridge, UK: BirdLife International, 2018).

477 15. Peters, H., O'Leary, B.C., Hawkins, J. P., Carpenter, K. E., Roberts, C.M. Conus: first comprehensive conservation red list assessment of a marine gastropod mollusc genus. PLoS One 8, e83353 (2013).

480 16. IUCN Standards and Petitions Committee. Guidelines for Using the IUCN Red List Categories and Criteria. Version 15.1 https://www.iucnredlist.org/documents/RedListGuidelines.pdf (2022).

483 17. Bower, D. S. et al. Island of opportunity: can New Guinea protect amphibians from a globally emerging pathogen? Front. Ecol. Environ. 17, 348-354 (2019).

485 18. CSIRO and Bureau of Meteorology. State of the Climate 2022. Government of Australia. https://www.csiro.au/en/research/environmental-impacts/climate-change/State-of-the-Climate (2022).

488 19. Winter, M. et al. Patterns and biases in climate change research on amphibians and reptiles: a systematic review. Royal Society Open Science, 3, 160158 (2016).

490 20. U.S. Global Change Research Program. Impacts, risks, and adaptation in the United States: Fourth National Climate Assessment. Volume 2 https://nca2018.globalchange.gov/downloads (2018).
21. Hof, C., Araújo, M., Jetz, W. & Rahbek, C. Additive threats from pathogens, climate and land-use change for global amphibian diversity. *Nature* **480**, 516–519 (2011).

22. United Nations Environment Programme. *Spreading like Wildfire – The Rising Threat of Extraordinary Landscape Fires. A UNEP Rapid Response Assessment*. UNEP, Nairobi (2022).

23. IUCN. *A Global Standard for the Identification of Key Biodiversity Areas*. Version 1.0. First edition (Gland, Switzerland: IUCN, 2016).

24. Urbina-Cardona, J. N. Conservation of Neotropical Herpetofauna: Research Trends and Challenges. *Trop. Cons. Sci.* **1**, 359–375 (2008).

25. Luther, D. et al. Global assessment of critical forest and landscape restoration needs for threatened terrestrial vertebrate species. *Glob. Ecol. and Cons. 24*, e01358 (2020).

26. Gilbert, M. J. et al. *Mitigating Batrachochytrium salamandrivorans in Europe. Batrachochytrium salamandrivorans Action Plan for European urodeles* http://bsaleurope.com/wp-content/uploads/2021/03/Bsal-Action-Plan.pdf (2020).

27. North American Bsal Task Force. *A North American strategic plan to prevent and control invasions of the lethal salamander pathogen Batrachochytrium salamandrivorans* www.salamanderfungus.org (2022).

28. García-Rodríguez, A. et al. Anticipating the potential impacts of Batrachochytrium salamandrivorans on Neotropical salamander diversity. *Biotropica* **54**, 157-169 (2022).

29. Machalaba C. & Karesh, W. B. Envisioning a world without emerging disease outbreaks. *Solutions* **6**, 63–71 (2015).

30. Zippel, K. et al. The amphibian ark: a global community for ex situ conservation of amphibians. *Herp. Cons. and Biol.* **6**, 340–352 (2011).
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35. IUCN SSC Amphibian Specialist Group *Amphibian Conservation Action Plan* (Wren, S. et al. eds.) https://www.iucn-amphibians.org/working-groups/thematic/ (2015).
## 526 **Figures**

527 **Fig. 1. Distribution of 2,872 globally threatened amphibian species.** Darker colours correspond to higher species richness. Colour scale based on 10 quantile classes. Maximum richness equals 528 61 species. Cell area is 865 km². One species is excluded because no spatial data is available.

530 **Fig. 2. Number of threatened amphibian species affected by major threats.** The major threats to a species were coded using the threats classification scheme and grouped for ease of comparison (see Methods sections 2.6 and 4.2). All threats shaded in green are causing habitat loss and degradation. Hatched areas denote the number of species for which the threat timing is in the future rather than ongoing. Note that most species are experiencing multiple threats.

535 **Fig. 3. Red List Indices (RLI) of all comprehensively assessed taxonomic groups on the IUCN Red List (a).** Amphibian-specific RLIs disaggregated by biogeographic realm (b), breeding strategy (c), and taxonomic order (d).

538 **Fig. 4. Geographical pattern of the primary drivers of deteriorating status among amphibians.** a, 482 species; 1980–2004. b, 306 species; 2004–2022. Cell colour is determined by the primary driver impacting the most species. Where two primary drivers equally contribute to a cell, an intermediate colour is shown. Stars indicate where the primary driver is undetermined or there are numerous primary drivers. Cell area is 7,775 km².

543 **Fig. 5.** Species listed into a higher Red List category are coded by the primary driver causing the change, for each time period. **a,** 1980–2004. **b,** 2004–2022. Red List categories are ordered by highest to lowest threat level: Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU) and Near Threatened (NT). CR species that are likely to be extinct have the Possibly Extinct tag (PE).
548 **Extended Data**

549 **Extended Data Fig. 1. Geographical pattern of 120 amphibians that improved in status**
550 **between 1980–2022.** Outlined hexagons indicate at least one species improved due to
551 conservation.

552 **Extended Data Table 1. Number of species in each Red List category for 1980, 2004, and**
553 **2022.** The 1980 and 2004 categories were determined by applying the backcasting methods
554 outlined in Butchart *et al.* (2007). The 2022 Red List categories are the results of the GAA2 study
555 and the most recent assessment for each species. The Critically Endangered (CR) category has an
556 additional option to tag a species as “Possibly Extinct (PE)” or “Possibly Extinct in the Wild
557 (PEW)”. The disaggregation of CR species has been provided in this table to emphasise the large
558 number of amphibians that are categorised as CR(PE).

559 Following the methods outlined in Section 4.1, the best, lower, and upper estimate of the
560 percentage of threatened or extinct species is calculated for each point in time. There has been a
561 steady increase in the percentage of threatened amphibians from 37.9% (1980) to 39.4% (2004) to
562 40.7% (2022). It should be noted that the two time periods (1980–2004 and 2004–2022) are not
563 equal; the first one being 24 years and the second only 18. From 1980 to 2004, an additional 118
564 species were categorised as threatened. An additional 90 species are threatened as of 2022. From
565 1980 to 2004, the total number of species listed as VU and EN decreased, while the number listed
566 as CR considerably increased from 588 to 766. In 1980, 24 species were considered CR(PE), but
567 by 2004 the number of CR(PE) species rose to 162. The number of species declared EX also
568 increased from 23 in 1980, to 33 in 2004. In contrast, from 2004 to 2022, the number of species in
569 each of the threatened categories increased by a similar amount; the number of CR(PE) species
increased by 23; and the number of EX species increased by four, which is substantially less than
the previous time period, but still of significant conservation concern.

**Extended Data Table 2.** Species with status deteriorations in each time period (1980–2004 and 2004–2022). Species are categorised by the primary driver of the status deterioration. Primary drivers are grouped in the first column and separated in the second.

**Extended Data Table 3.** Number of species with status deteriorations in each time period (1980–2004 and 2004–2022) disaggregated by the data groupings used to calculate the Red List Indices and primary drivers of status deteriorations.

In the Neotropics, disease stands out as by far the most common driver of status deteriorations between 1980–2004 (250 species), but this driver diminished between 2004–2022 (45 species). Climate change effects were only implicated for one species in the Neotropics between 1980–2004 but increased substantially to 91 species between 2004–2022. A similar trend is shown in the Nearctic and Australasia/Oceania. Interestingly, the Afrotropical region shows the reverse trend for disease, with the number of species deteriorating in status increasing from three in the first time period to 11 in the second, due to recent *Bd* outbreaks emerging in central and eastern Africa. In the Palearctic, the increasing impact of disease is also noticeable, and can be attributed to the recent introduction of *Bsal* and the impact its predicted spread will have on many salamanders.

For Anura, the impact of disease has greatly diminished with time, and climate change effects have more recently emerged as the most common primary driver, although habitat loss/degradation is still prominent. With the emergence of *Bsal*, disease has remained an overall concern for Caudata, although climate change effects are now also considered the most common primary driver. The
trend of diminishing impacts due to disease in the first period, and the emergence of climate change

effects in the second period seems to be similar for both larval and direct developers.
593

# Methods

594

## 1. Data Compilation

595

596

597

598

The Amphibian Red List Authority (ARLA) of the IUCN SSC Amphibian Specialist Group (ASG) coordinated the GAA2 according to the ASG's groupings of countries into regional working groups (Supplementary Table 2). Only a subset of the ASG regions were actively updating assessments at any one time.

599

600

601

602

Each regional assessment process addressed the endemic and non-endemic species in four stages: 1) Pre-assessment, 2) Expert consultation, 3) Assessment finalising and consistency checks, and 4) Review. After the four stages were completed for all regions, the ARLA team retrospectively assigned a Red List category to all species for the years 1980 and 2004 (see section 2.8).

603

### 1.1 Pre-Assessment

604

605

606

The GAA2 comprises reassessments of the 5,743 GAA1 species and the majority of species described and assessed for the first time between the two GAA projects (2004–2011). The GAA2 also contains an additional 2,286 newly described species assessed for the first time.

607

608

609

Regional species lists were compiled, incorporating taxonomic changes and new species descriptions collated by Amphibian Species of the World³⁹. Literature reviews were conducted and any new published information was incorporated into draft assessments.

610

611

612

613

A particular challenge to this project is the dynamic state of amphibian taxonomy. By 2022, 191 of the GAA1 species had been synonymized, 24 were no longer considered valid species, three were considered hybrids and hence ineligible for reassessment, and four had been unintentionally assessed twice under different names.
## 1.2. Expert Consultation

Over 1,000 subject-matter experts provided information to complete the required assessment fields (see Extended Acknowledgements in the Supplementary Information). Expert consultation of draft assessments was achieved through 31 in-person workshops, three virtual workshops with over 180 online meetings, as well as phone and email correspondence (see Supplementary Note 2). A considerable amount of effort went into engaging with a diversity of experts across several axes (e.g., gender, age, geography, type of expertise) so as to reach the widest range of experts as possible and minimise reliance on any individual expert.

When uncertainty in the data and differences in risk tolerance between contributing experts was encountered, this was captured in the assessment as a range of possible values or scenarios. Where available, the data quality fields were recorded using standardised data qualifiers (e.g. current population trend data derivation). For more information, see Data Quality chapter in the IUCN Red List Guidelines. In many cases where direct observational data were not available, data fields (e.g., population size and severity of threats) were derived through expert estimation or inference using basic facilitation techniques.

## 1.3. Assessment Finalising

The supporting data and Red List categories were finalised by an ARLA team member who also performed checks to ensure the IUCN categories and criteria were applied in a consistent manner to the species within a particular region, but also between ASG regions. Consistency was also sought for species with similar traits or co-occurring species.

## 1.4. Review

An independent reviewer ensured biological accuracy and correct and consistent application of the
636 Red List criteria. This process involved fifteen independent reviewers between 2012–2022 (see
637 Extended Acknowledgements in the Supplementary Information). The IUCN Red List Unit also
638 reviewed assessments for appropriate application of the criteria.

639 **2. Data Collected**

640 Species assessments are required to meet the minimum documentation standards of the IUCN Red
641 List as outlined in the Supporting Information Guidelines
642 (https://www.iucnredlist.org/resources/supporting-information-guidelines). The supporting
643 information includes information on distribution, population, habitat preferences, ecology, use and
644 trade, threats, conservation measures as well as the IUCN Red List Category and Criteria. Each
645 assessment also includes a bibliography and the names of people involved in the process. This
646 section details the supporting data collected for each species.

647 **<u>2.1 Systematics</u>**

648 Higher taxonomy and scientific name, taxonomic authority, major synonyms, common names, and
649 taxonomic notes (if pertinent) were collected.

650 Occasionally, data from experts supports an alternative taxonomic arrangement from that of the
651 Amphibian Species of the World³⁶, which were accepted only in well-justified circumstances.
652 Departures from Amphibian Species of the World are documented in the ‘Taxonomic Notes’ field
653 of an assessment.

654 **<u>2.2 Summary Information</u>**

655 Narrative texts about geographic range, population, habitat and ecology (including breeding and
656 non-breeding habitats, as well as breeding strategy), threats, and conservation and research
measures are required.

## 2.3 Breeding Strategy

The breeding strategy of each amphibian was recorded in SIS based on whether they 1) lay eggs; 2) give birth to live young; 3) exhibit parthenogenesis; 4) have a free-living larval stage; and/or 5) require water for breeding. When appropriate, a species' breeding strategy was inferred from one or more congeners. Species were categorised as either larval developers, direct-developers, live-birth or unknown for the purpose of this study, as follows:

* **Larval developers (5,316 species):** species coded as laying eggs and having a free-living larval stage.

* **Direct developers (2,452 species):** species coded as laying eggs but do not have a free-living larval stage.

* **Live birth (61 species):** species coded as giving birth to live young (viviparity) regardless of whether they have a free-living larval stage.

* **Unknown (182 species):** species coded as unknown for one or more questions which prevented their breeding strategy from being categorised.

## 2.4 Distribution Map

A map representing the currently known distribution of each species was generated following the IUCN Mapping Standards (https://www.iucnredlist.org/resources/mappingstandards). The limits of a species' distribution were mapped using known occurrences of the taxon, and knowledge of habitat preferences, elevation limits, etc. Standard data attributes on presence, origin, and seasonality were recorded for each range polygon. There are 53 species in the GAA2 without distribution maps as their distribution is too poorly known.
679 **2.5 Additional Distribution Data**
680 Occurrences in biogeographic realms³⁷, biodiversity hotspots³⁸, countries, and states or provinces
681 (where required) were coded.

682 **2.6 Classification Schemes**
683 To allow for comparative analyses and to ensure uniformity across species, a series of
684 Classification Schemes were used (https://www.iucnredlist.org/resources/classification-schemes)
685 for Habitats, Threats, Conservation Actions, Research Needed and Use and Trade.

686 **2.7 Red List Category and Criteria**
687 The IUCN Red List criteria were applied to the supporting data and the appropriate Red List
688 category was determined, supported by a rationale
689 (https://www.iucnredlist.org/resources/categories-and-criteria). A statement of the reason(s) for
690 change in category from the previous assessment was documented for reassessed species. The date
691 of assessment and the names of the facilitators, compilers, and contributors were recorded.

692 **2.8 Backcasting Red List Categories**
693 Only genuine changes in Red List category should be considered when comparing extinction risk
694 in amphibians over time. A genuine change is either a real improvement or deterioration in the
695 status of a species, driven by changes in the threat(s). For example, the protection of a species'
696 habitat that halted the primary threat of deforestation could result in a genuine status improvement.
697 On the other hand, a genuine status deterioration could be due to population declines associated
698 with the introduction of a disease, the start of human activities causing ongoing habitat loss and
699 degradation, or the projected effects of climate change.
The majority of category changes from GAA1 to GAA2 were for non-genuine reasons. Generally, these were the result of the new information, such as distributional changes or clarity on threatening processes. For example, if a species was previously considered a narrow range endemic but subsequently found much more widespread, the resulting change to a lower extinction risk category would be considered non-genuine. Other non-genuine reasons for category changes included changes in the application of the criteria or incorrect data used in the previous assessment(s).

Stuart *et al.* (2004) relied on the knowledge available at that time to backcast their 2004 assessments to 1980. This year corresponded approximately to the timeframe of severe population declines, as they were understood at the time. The GAA1 backcasted dataset provides a historical perspective taken into consideration in the GAA2 backcasting.

In early 2022, the ARLA team backcasted the GAA2 categories to 1980 and 2004 following the method outlined in Butchart *et al.* (2007). This method uses the information in the Red List assessments in combination with additional knowledge on threatening processes, habitat decline trends, and conservation actions (and in some cases further expert consultation) to determine whether a genuine change in a species' Red List category is likely to have occurred between 1980–2004 and 2004–2022. In the absence of significant evidence suggesting a genuine change, the GAA2 Red List category was assumed to be the same for previous time periods. Data Deficient (DD) species were automatically backcasted as DD in 1980 and 2004. The Supplementary Information Data 1 file contains the list of species that have deteriorated in status along with their backcasted categories, while Supplementary Information Data 2 file contains the list of species that have improved in status.
722 **2.9 Primary Drivers**

723 During the backcasting process, for species considered to have undergone a genuine category
724 change since 1980, the relative importance of documented threats for each species was estimated.

725 The most significant perceived threat was assigned as the “primary driver” and selected from the
726 following list: agriculture, mining/energy production, infrastructure development, human
727 disturbance, timber and plant harvesting, anthropogenic fire, water management, native species,
728 introduced species, pollution, geological events, disease, over-exploitation, climate change effects,
729 and undetermined.

730 Species that deteriorated in status were assigned the primary driver that contributed to the category
731 change. For species that improved in status, the primary driver that was previously causing the
732 deterioration but has since been mitigated were assigned. Improvements that were the result of
733 conservation action were documented through an additional data field (Supplementary Information
734 Data 1 and 2).

735 **3. Data Limitations**

736 **3.1 Regional Variation**

737 IUCN Red List assessments are considered out of date ten years after the date of assessment.

738 Therefore, all species included in the GAA2 have been assessed within the past ten years and are
739 considered current. For regions that were assessed earlier in the GAA2, however, the data are
740 comparatively less current than for the regions completed during the latter stages of the project.

741 For example, toward the end of the GAA2, the severity, scope, and timing of the effects of climate
742 change were at the forefront of discussions but were not as well-addressed for earlier regions.
743 Thus, the species- and habitat-specific effects of climate change are likely underestimated for 744 regions assessed earlier in the GAA2.

745 Data scarcity was a common issue for regions with few herpetologists and for species occurring in 746 areas that are difficult to access. As such, assessments in data-poor regions, such as Melanesia and 747 sub-Saharan Africa, generally contain significantly less detail than data-rich regions such as North 748 America, Australia, and Europe, where species are often relatively well-studied. This is also true 749 for population data, where there has been little (if any) population monitoring, and threat- 750 determining processes with scarce published literature on climate change, rates of habitat loss, or 751 exploitation.

752 The rate of new species descriptions also varies regionally, with the amphibian fauna in many parts 753 of the world still very poorly known. Hence the currently known amphibian richness and diversity 754 is significantly underestimated in those places.

### 3.2 Not Evaluated Species

755 The GAA2 aimed to assess the extinction risk of all taxonomically valid amphibian species. 756 However, as the annual rate of new species descriptions remains high, inevitably some newly 757 described species are not included in the GAA2. After a region had been completed during the 758 GAA2, all subsequent new species descriptions for that region were reserved for the GAA3. On 759 occasion, a few species were assessed after the Red List update for a region was no longer active 760 — typically when a species was known to be facing serious threats or there were taxonomic 761 implications for regions that were actively being updated. As of December 2022, the number of 762 new species waiting to be assessed in the GAA3 was approaching 400 and is steadily increasing 763 as new species descriptions are published weekly.
### 3.3 Data Deficient Species

In the GAA2, 909 species were categorised as DD because of insufficient data. At a minimum, DD species are expected to be threatened at a similar proportion as the global average of threatened species (40.7%). Due to these data gaps, we expect the number of genuine changes to also be underestimated. This may be the case for DD species that have not been surveyed for decades and for which there is no information to confirm whether population declines have taken place.

## 4. Analytical Methods

### 4.1 Percentage of Threatened Species

Species in the Critically Endangered (CR), Endangered (EN), and Vulnerable (VU) categories are referred to as “threatened” species.

When determining the percentage of threatened species in this study, a best estimate was calculated excluding the number of DD and EX species from the total. However, Extinct in the Wild (EW) species were included because there remains the possibility that they can be reintroduced to the wild. To capture the uncertainty within this estimate, a lower estimate was calculated by assuming all DD species are not threatened, and an upper estimate is calculated by assuming all DD species are threatened:

$$781 \quad \textit{Lower Estimate} = (EW + CR + EN + VU)/(total \ species - EX)$$

$$782 \quad \textit{Best Estimate} = (EW + CR + EN + VU)/(total \ species - EX - DD)$$

$$783 \quad \textit{Upper Estimate} = (EW + CR + EN + VU + DD)/(total \ species - EX)$$

For further details and discussion of these methods, see the IUCN Red List Resources Summary Statistics documentation (https://www.iucnredlist.org/resources/summary-statistics).
786 **4.2 Threats to Threatened Species**

787 The GAA2 coded threats affecting amphibians using the threats classification scheme (see Section 2.6). When relevant, more than one threat was coded per species. The timing of the threat (past, ongoing, future), and the resulting stresses to the species, were also indicated.
788
789

790 In Fig. 2, the hierarchy within the threats classification scheme was used to group similar threats
791 and allow for comparison, although some, such as Bd, were separated to highlight their
792 significance. Only “ongoing” major threats to threatened species are included. The exception being
793 when Bd, Bsal, and climate change effects were coded as future threats only. To highlight the
794 emerging nature of these threats, the number of threatened species are indicated by hatching on
795 the bars.

796 Threats groupings were as follows:

797 • **Agriculture**: All codes under 2 Agriculture & aquaculture.

798 • **Timber and plant harvesting**: All codes under 5.2 Gathering terrestrial plants and 5.3
799 Logging and wood harvesting.

800 • **Infrastructure development**: All codes under 1 Residential & commercial development
801 and 4 Transportation & service corridors.

802 • **Pollution**: All codes under 9 Pollution.

803 • **Mining/energy production**: All codes under 3 Energy production & mining.

804 • **Water management**: All codes under 7.2 Dams & water management.

805 • **Human disturbance**: All codes under 6 Human intrusions & disturbance.

806 • **Geological events**: All codes under 10 Geological events.
807 • **Over-exploitation:** All codes under 5.1 Hunting & collecting terrestrial animals and 5.4
808 Fishing & harvesting aquatic resources.

809 • **Climate change:** All codes under 11 Climate change & severe weather.

810 • **Fire:** All codes under 7.1 Fire & fire suppression.

811 • **Bd:** Under the codes 8.1.2 Invasive non-native/alien species/diseases - Named species and
812 8.4.2 Problematic species/diseases of unknown origin - Named species, the name of
813 invasive/problematic species must be recorded. Only records for which *Bd* was listed were
814 included.

815 • **Bsal:** Under the codes 8.1.2 Invasive non-native/alien species/diseases - Named species
816 and 8.4.2 Problematic species/diseases of unknown origin - Named species, the name of
817 invasive/problematic species must be recorded. Only records for which *Bsal* was listed
818 were included.

819 • **Invasive species:** All codes under 8.1 Invasive non-native/alien species/diseases, 8.3
820 Introduced genetic material, 8.4 Problematic species/diseases of unknown origin, 8.5
821 Viral/prion-induced diseases and 8.6 Diseases of unknown cause, except when the
822 invasive/problematic species is identified as *Bd* or *Bsal*.

823 • **Native species:** All codes under 8.2 Problematic native species/diseases.

824 **4.3 Red List Index**

825 Determining trends in the extinction risk of amphibians requires that only genuine changes in the
826 Red List category between assessments be included in the RLI. Therefore, the backcasted 1980
827 and 2004 categories assigned in the GAA2 (Section 2.8, Extended Data Table 1) are used to
828 calculate the Red List Index (RLI) for amphibians.
The RLI is calculated following the methods outlined in Butchart *et al.* (2007) and detailed in https://www.iucnredlist.org/assessment/red-list-index. The value of the RLI at each data point is an indication of the average extinction risk of all species at that point in time and can range from 0 (all species are Extinct) to 1 (all species are Least Concern). The gradient (slope) of the line is a measure of the rate of change in Red List categories. Thus, a steep negative gradient would indicate that a considerable proportion of species moved from a less threatened to a more threatened Red List category. In contrast, a positive gradient is indicative of an overall improvement.

It is important to note that CR(PE) and EX species are weighted the same when calculating the RLI. Hence a change in category from CR(PE) to EX from one time period to the next is not considered a deterioration in status, however, a change from CR to CR(PE) is treated as such. Data Deficient species are not included in the RLI as their extinction risk is still unknown.

The RLIs for other comprehensively assessed taxonomic groups are included in Fig. 2a to allow for a direct comparison with amphibians. The relatively small number of amphibians (264) occurring across more than one biogeographic realm were included in the disaggregated RLI calculations of each realm of occurrence (Fig. 3b). This is considered the best approach for representing the overall extinction risk of a given realm.

The decline in the amphibian RLI could initially be interpreted as minimal. To put this trend into perspective, however, 482 amphibians moved into a higher extinction risk category between 2004–2022 and 306 between 1980–2004 (Extended Data Table 2).

## 4.4 Grouping of Primary Drivers

For species that changed categories between assessment periods, a “primary driver” responsible for the change was allocated (Section 2.9, Supplementary Information Data 1). Many of these
primary drivers cause habitat loss and degradation (i.e., “habitat loss/degradation”). For the purpose of this study, the drivers were further grouped as follows:

* **Habitat loss/degradation:** agriculture, mining/energy production, infrastructure development, human disturbance, timber and plant harvesting, anthropogenic fire, water management, native species, pollution, geological events.

* **Disease:** chytridiomycosis only.

* **Over-exploitation:** over-exploitation only.

* **Climate change effects:** climate change effects only.

* **Undetermined:** includes a small number of species for which there is insufficient information regarding what is/are the driver(s) of the change in category.

* **Numerous:** includes a small number of species (5) that have more than one driver that are considered to be contributing equally to the change in category.

Invasive species are documented as a threat to 415 threatened species (Fig. 2). However, except for the species likely affected by the amphibian chytrid fungus, Bd, no amphibians in this study experienced a deterioration in status because of invasive non-native species. A small number of category changes were driven by the threats “native species”, “geological events”, and “anthropogenic fire” which cause habitat degradation and were, therefore, grouped under “habitat loss/degradation”.

Over-exploitation was the primary driver for 31 status deteriorations during 1980–2004 compared to only four during 2004–2022 (Extended Data Table 2). Deteriorations in status due to over-exploitation remain concentrated in Indomalaya (Extended Data Table 3) – particularly in eastern and southeastern Asia (Fig. 4). However, population declines due to over-exploitation are typically based on expert opinion because very little data exist on utilisation rates of amphibians. As a result,
it was often difficult to accurately determine when and to what degree a species deteriorated in status.

## Methods References

36. Frost, D. R. *Amphibian Species of the World: an Online Reference*.

https://amphibiansoftheworld.amnh.org/index.php (2023).

37. Olson, et al. Terrestrial Ecoregions of the World: A New Map of Life on Earth: A new global map of terrestrial ecoregions provides an innovative tool for conserving biodiversity. *BioScience*, 51, 933–938.

38. Critical Ecosystem Partnership Fund. *Biodiversity Hotspots Defined*.

https://www.cepf.net/our-work/biodiversity-hotspots/hotspots-defined (2023).

## Data and Materials Availability

The spatial and additional tabular data will be available in a centralised repository on the IUCN Red List website (link to be provided). Assessment data, including range maps, are already publicly available on the IUCN Red List of Threatened Species™ website (https://iucnredlist.org) for most species, in particular for regions that were completed earlier in the GAA2. All 8,011 assessments completed during the GAA2 will be available on this website following its July 2023 update (version 2023–1). In rare cases, a species may be threatened because of over-collection and sensitive distribution information is not publicly available.
892 Acknowledgements

893 General

894 We are grateful to each of the contributors named in the Supplementary Information; and Don
895 Church, Wes Sechrest, Pria Ghosh, Jon Paul Rodriguez, Kira Mileham, and Resit Akcakaya
896 without whom the GAA2 would have not been possible.

897 The views expressed in this publication do not necessarily reflect those of IUCN's staff, Members,
898 or Commissions. The designation of geographical entities in this paper, and the presentation of the
899 material, do not imply the expression of any opinion whatsoever on the part of IUCN concerning
900 the legal status of any country, territory, or area, or of its authorities, or concerning the delimitation
901 of its frontiers or boundaries.

902 Funding

903 The majority of funds were provided by Re:wild, Synchronicity Earth, Kering, and the
904 Environment Agency - Abu Dhabi Framework Grant to the IUCN Species Survival Commission
905 (SNS, JAL, PL, BL). Grants for specific components of the GAA2 are listed below.

906 Alashan SEE Foundation grant The IUCN Red List Workshop for Chinese Amphibian Species
907 (JAL, LH)

908 Detroit Zoological Society grant Catalyzing Amphibian Conservation in Honduras (JAL, KN, LH,
909 PL)

910 Detroit Zoological Society grant Support to the IUCN SSC Amphibian Red List Authority for the
911 Updates of Madagascar and the Tropical Americas (JAL, AA)

912 Dilmah Conservation grant Updating the IUCN Red List Assessments for the Amphibians of Sri

913 Lanka (JAL, KN, LH, PL)
914 Honolulu Zoo grant Support to Amphibian Conservation in Southeast Asia (JAL, AA)

915 Red List Committee allocation of funds raised in 2015, 2016, 2017, 2018, 2019, 2020 via the

916 Integrated Biodiversity Assessment Tool (IBAT) to the IUCN SSC Amphibian Specialist Group

917 Red List Authority (JAL, SNS, PL, BL, KN, LH)

918 Kering grant Critical Biodiversity Information for Decision-Making (JAL, PL, KN, LH)

919 Museo delle Scienze di Trento to the IUCN SSC Amphibian Specialist Group Red List Authority

920 (JAL, AA)

921 NatureServe grant Andean Species-level Indicators (JAL, KN, LH)

922 Rainforest Trust grant Identifying Priority Sites for the Most Threatened Amphibian Species (JAL,

923 KN, LH, SNS)

924 Yayasan Belantara grant support for the Indonesian Amphibian Red List Assessment Workshop

925 (MDK, AH)

926 **Partner and Collaborating Organisations**

927 In addition to the many institutions that hosted workshops and provided the time of their staff to
928 participate in the GAA2, we recognize the unique contributions of the following organisations:

929 • American Museum of Natural History's Amphibian Species of the World

930 • Re:wild

931 • IUCN Biodiversity Assessment Unit

932 • Amphibian Survival Alliance

933 • IUCN SSC Chair's Office

934 • Red List Technical Working Group

935 • Amphibian Ark

936 • NatureServe
937 • Synchronicity Earth

938 • iNaturalist

939 **IUCN Red List Unit**

940 Serving as the gatekeeper to the Red List, the IUCN Red List team provided technical training and

941 support, maintenance of the online SIS database, assessment checks, and publication of

942 assessments on the Red List website. We recognize in particular the contributions of Ackbar Joolia,

943 Ana Martinez Richardt, Caroline Pollock, Craig Hilton-Taylor, Janet Scott, and Jemma Window.

944 **Extended Acknowledgements**

945 The GAA2 was an extensive collaboration of over 1,000 individuals. The co-authors of this paper

946 acknowledge their contributions and have listed their contributions individually in the Extended

947 Acknowledgements section of the Supplementary Information.
948 **Author contributions**

949 Conceptualization: JAL, JC, KN, LH, BL, PL, SNS

950 Methodology: JAL, JC, KN, LH, CHT, BL, PL, SNS

951 Validation: JAL, JC, KN, LH, CHT, BL, PL, SNS

952 Formal analysis: JC, KN, CHT

953 Investigation: JAL, JC, KN, LH, AAK, AAn, AAo, AB, AC, ACD, AF, AFG, AH, AJ, AMS, AOM, AS, ASB, AT, BG, BS, BT, CA, CCMR, CFCF, CHT, CJH, CRVA, CSe, CSR, CSt, DFCH, DHO, DJG, DJS, DLW, EN, ENM, ESHQ, FA, FBo, FBr, FEC, FG, FK, FSA, FX, GC, GFMR, GGD, GPO, HMOA, ID, IFM, IRD, JCI, JHY, JJ, JJLR, JM, JNUC, JTW, KO, KOC, KV, KVG, LCM, LCW, LFT, LMD, MAP, MDK, MEA, MF, MFA, MFN, MHYM, ML, MMa, MMe, MMHK, MOR, MR, MS, MV, NG, NGK, NLG, PAB, PJRK, PW, PYI, RAB, RI, RJA, RLJ, RvM, SBH, SD, SDB, SG, SJI, SJR, SJRH, SLA, SP, SPL, SRG, SVF, SW, THC, TON, TPC,

960 TPFAJ, TQN, TRC, TS, TWP, UK, ZY

961 Data Curation: JAL, JC, KN, LH, CHT, EN, LCW, NG, TPFAJ

962 Writing - Original Draft: JAL, JC, KN, LH, BL, PL, SNS
963 Writing - Review & Editing: JAL, JC, KN, LH, AAK, AAn, AAo, AB, AC, ACD, AF, AFG, AH, AJ, AMS, AOM, AS, ASB, AT, BG, BS, BT, CA, CCMR, CFCF, CHT, CJH, CRVA, CSe, CSR, CSt, DFCH, DHO, DJG, DJS, DLW, EN, ENM, ESHQ, FA, FBo, FBr, FEC, FG, FK, FSA, FX, GC, GFMR, GGD, GPO, HMOA, ID, IFM, IRD, JCI, JHY, JJ, JJLR, JM, JNUC, JTW, KO, KOC, KV, KVG, LCM, LCW, LFT, LMD, MAP, MDK, MEA, MF, MFA, MFN, MHYM, ML, MMa, MMe, MMHK, MOR, MR, MS, MV, NG, NGK, NLG, PAB, PJRK, PW, PYI, RAB, RI, RJA, RLJ, RvM, SBH, SD, SDB, SG, SJI, SJR, SJRH, SLA, SP, SPL, SRG, SVF, SW, THC, TON, TPC, TPFAJ, TQN, TRC, TS, TWP, UK, ZY, BL, PL, SNS
971 Visualisation: JC, KN

972 Supervision: JAL, JC, CHT, BL, PL, SNS

973 Project administration: JAL, JC, KN, LH, AAn, AC, ACD, AMS, AS, AT, CA, CCMR, CFCF,

974 CRVA, CSe, DFCH, DHO, ENM, FA, FEC, FG, FX, GC, GPO, IFM, JCI, JJ, JJLR, JM, JNUC,

975 JTW, KO, KOC, KV, KVG, MDK, ML, MMa, MMe, MOR, MS, MV, NLG, RI, SBH, SJI, SJR,

976 SPL, SW, TPC, TWP, UK

977 Funding acquisition: JAL, KN, LH, ACD, FA, JJLR, JM, MDK, BL, PL, SNS

978 **Competing Interests**

979 Authors declare that they have no competing interests.

980 **Materials and correspondence**

981 Correspondence and material requests should be addressed to Jennifer A. Luedtke

982 (jluedtke@rewild.org).

983
<figure><img src="image_2.png" /></figure>

Number of species
1 61
<figure><img src="image_3.png" /></figure>
<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>
<figure><img src="image_8.png" /><figcaption>b</figcaption></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>
a 1980-2004

<figure><img src="image_11.png" /></figure>

b 2004-2022

<figure><img src="image_12.png" /></figure>

Category at end of time period
<figure><img src="image_13.png" /></figure>

Number of species

1-3

4-6

7-13
<table><thead><tr><th>Red List Category</th><th>1980</th><th>2004</th><th>2022</th></tr></thead><tbody><tr><td>EX</td><td>23</td><td>33</td><td>37</td></tr><tr><td>EW</td><td>0</td><td>1</td><td>2</td></tr><tr><td>CR(PEW)</td><td>0</td><td>1</td><td>1</td></tr><tr><td>CR(PE)</td><td>24</td><td>162</td><td>185</td></tr><tr><td>CR</td><td>564</td><td>604</td><td>612</td></tr><tr><td>EN</td><td>1,293</td><td>1,235</td><td>1,264</td></tr><tr><td>VU</td><td>800</td><td>786</td><td>811</td></tr><tr><td>NT</td><td>384</td><td>413</td><td>451</td></tr><tr><td>LC</td><td>4,014</td><td>3,868</td><td>3,739</td></tr><tr><td>DD</td><td>909</td><td>909</td><td>909</td></tr></tbody></table>

<table><thead><tr><th>Percentage of Species Threatened</th><th>Lower estimate</th><th>Best estimate</th><th>Upper estimate</th></tr></thead><tbody><tr><td></td><td>33.6</td><td>37.9</td><td>44.9</td></tr><tr><td></td><td>35.0</td><td>39.4</td><td>46.3</td></tr><tr><td></td><td>36.1</td><td>40.7</td><td>47.5</td></tr></tbody></table>
<table><thead><tr><th>Grouped driver</th><th>Primary driver</th><th>1980-2004</th><th>2004-2022</th></tr></thead><tbody><tr><td>Disease</td><td></td><td>281</td><td>69</td></tr><tr><td>Habitat loss/ degradation</td><td></td><td>156</td><td>112</td></tr><tr><td></td><td>Agriculture</td><td>93</td><td>57</td></tr><tr><td></td><td>Mining/energy production</td><td>22</td><td>27</td></tr><tr><td></td><td>Infrastructure development</td><td>19</td><td>11</td></tr><tr><td></td><td>Timber and plant harvesting</td><td>9</td><td>1</td></tr><tr><td></td><td>Water management</td><td>8</td><td>4</td></tr><tr><td></td><td>Human disturbance</td><td>2</td><td>2</td></tr><tr><td></td><td>Anthropogenic fire</td><td>1</td><td>5</td></tr><tr><td></td><td>Pollution</td><td>1</td><td>1</td></tr><tr><td></td><td>Geological events</td><td>1</td><td>1</td></tr><tr><td></td><td>Native species</td><td>0</td><td>3</td></tr><tr><td>Over-exploitation</td><td></td><td>31</td><td>4</td></tr><tr><td>Climate change effects</td><td></td><td>6</td><td>119</td></tr><tr><td>Undetermined</td><td></td><td>6</td><td>1</td></tr><tr><td>Numerous</td><td></td><td>2</td><td>1</td></tr><tr><td>Total</td><td></td><td>482</td><td>306</td></tr></tbody></table>
<table><thead><tr><th rowspan="2">Data grouping</th><th rowspan="2">Time period</th><th rowspan="2">Disease</th><th colspan="4">Primary driver</th></tr><tr><th>Habitat loss/ degradation</th><th>Over-exploitation</th><th>Climate change effects</th><th>Numerous</th></tr></thead><tbody><tr><td rowspan="2">Afrotropics</td><td>1980–2004</td><td>3</td><td>12</td><td>1</td><td>0</td><td>0</td></tr><tr><td>2004–2022</td><td>11</td><td>3</td><td>0</td><td>4</td><td>0</td></tr><tr><td rowspan="2">Australasia/ Oceania</td><td>1980–2004</td><td>25</td><td>4</td><td>0</td><td>4</td><td>0</td></tr><tr><td>2004–2022</td><td>2</td><td>8</td><td>0</td><td>11</td><td>0</td></tr><tr><td rowspan="2">Indomalaya</td><td>1980–2004</td><td>0</td><td>3</td><td>9</td><td>0</td><td>0</td></tr><tr><td>2004–2022</td><td>0</td><td>5</td><td>1</td><td>0</td><td>1</td></tr><tr><td rowspan="2">Nearctic</td><td>1980–2004</td><td>4</td><td>10</td><td>0</td><td>1</td><td>0</td></tr><tr><td>2004–2022</td><td>0</td><td>5</td><td>0</td><td>12</td><td>0</td></tr><tr><td rowspan="2">Neotropics</td><td>1980–2004</td><td>250</td><td>114</td><td>4</td><td>1</td><td>2</td></tr><tr><td>2004–2022</td><td>45</td><td>77</td><td>0</td><td>91</td><td>0</td></tr><tr><td rowspan="2">Palaearctic</td><td>1980–2004</td><td>0</td><td>26</td><td>12</td><td>0</td><td>0</td></tr><tr><td>2004–2022</td><td>11</td><td>16</td><td>2</td><td>1</td><td>0</td></tr><tr><td rowspan="2">Larval developer</td><td>1980–2004</td><td>203</td><td>107</td><td>31</td><td>1</td><td>2</td></tr><tr><td>2004–2022</td><td>51</td><td>65</td><td>4</td><td>42</td><td>1</td></tr><tr><td rowspan="2">Direct developer</td><td>1980–2004</td><td>76</td><td>45</td><td>0</td><td>5</td><td>0</td></tr><tr><td>2004–2022</td><td>15</td><td>47</td><td>0</td><td>73</td><td>0</td></tr><tr><td rowspan="2">Live birth</td><td>1980–2004</td><td>1</td><td>3</td><td>0</td><td>0</td><td>0</td></tr><tr><td>2004–2022</td><td>3</td><td>0</td><td>0</td><td>2</td><td>0</td></tr><tr><td rowspan="2">Anura</td><td>1980–2004</td><td>272</td><td>139</td><td>23</td><td>5</td><td>2</td></tr><tr><td>2004–2022</td><td>57</td><td>89</td><td>1</td><td>103</td><td>1</td></tr><tr><td rowspan="2">Caudata</td><td>1980–2004</td><td>9</td><td>15</td><td>8</td><td>1</td><td>0</td></tr><tr><td>2004–2022</td><td>12</td><td>22</td><td>3</td><td>16</td><td>0</td></tr><tr><td rowspan="2">Gymnophiona</td><td>1980–2004</td><td>0</td><td>2</td><td>0</td><td>0</td><td>0</td></tr><tr><td>2004–2022</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td></tr></tbody></table>