Crop diversity needed today for tomorrow’s food security and nutrition

Science can help mitigate, stem, and reverse loss of genetic diversity, for better productivity, resilience, and adaptive capacity of agriculture, new study shows.

Although scientists have been ringing bells for more than 100 years about the decline of crop diversity in agriculture, questions about the magnitude, causes, and significance of this loss remain unanswered.

A team of 15 scientists, including Stef de Haan from the International Potato Center, set out 18 months ago to answer these persisting questions, resulting in the largest review ever conducted of evidence about change in crop diversity over time worldwide. The team reviewed hundreds of primary literature sources published over the last 80nyears that examine potential crop diversity loss, also called “genetic erosion”. The global collaborative effort found that 95% of all studies reported diversity change, and almost 80% found evidence of loss.

Economic, agricultural, technological, climatic, and political changes during the last 100 years have together led to the decline or disappearance of diversity important to agriculture, both from cultivated fields and from wild habitats. Much of the crop diversity that remains continues to face the threat of erosion or even extinction, while also becoming more homogenous across local landscapes and around the world. 

“The global picture that emerges from our review is that of enormous loss over a relatively short period of time of traditional agricultural diversity, which was nurtured by many cultures around the world over the last 10,000 years,” said lead author Colin Khoury, Senior Director for Science and Conservation at San Diego Botanic Garden and research scientist at the Alliance of Bioversity International and the International Center for Tropical Agriculture (CIAT). “Yet the picture also provides hope, as considerable crop diversity persists, and because it shows that agriculture can be re-diversified.”

Khoury collaborated with scientists at international and national agricultural research centers in the USA, Colombia, Germany, Italy, Mexico, and Peru, as well as universities including El Colegio de la Frontera Sur (Chiapas, Mexico), Ohio State University, Saint Louis University, the University of Arizona, the University of California at Davis, the University of Cambridge, and the University of Illinois to carry out the study, “Crop genetic erosion: understanding and responding to loss of crop diversity, published today in New Phytologist as a prestigious Tansley review. This review series was named after the famous English botanist and ecologist Arthur Tansley, who coined the term ecosystem in 1935.

Crop diversity is a critically important resource for agriculture and for human nutrition. This diversity keeps crops productive as they face pests and diseases, provides resilience during extreme weather and other shocks, and offers the potential to adapt to changing climates and meet new market demands. In contributing to crop productivity and also to dietary diversity, it underpins food security and nutrition

“The magnitude of crop diversity loss we have seen in some regions of the world underscores the importance of conserving this diversity outside of these ecosystems as well as within them,” said Luigi Guarino, Director of Science at the Crop Trust, and one of the study’s authors. ”Collections of crop diversity such as those in agricultural genebanks and botanic gardens can mitigate local and regional losses, enable the future reestablishment of diversity on farms, and preserve the availability of crops for future use by all. We need to strengthen these repositories and duplicate unique collections in other locations to insure against the risk of loss,” he said. 

There are currently approximately 1,750 genebanks worldwide, maintaining over seven million samples of crop diversity, with botanic gardens, universities, nonprofits, community seedbanks, and local conservation networks further contributing to ex situ conservation. However, more work is needed to conserve the full range of diversity at risk of disappearing from farmers’ fields and (in the case of crop wild relatives, the wild progenitors and cousins of cultivated plants) from grasslands, forests and other natural habitats. 

The study analyzed change in diversity of traditional crop varieties, or landraces, cultivated on farms; of modern crop cultivars in agriculture; of crop wild relatives in their natural habitats; and of crop genetic resources held in ex situ conservation repositories. The extent of change over time in these environments, while considerable, varied by crop, location, and analytical approach. 

“The good news is that while we found evidence of enormous diversity loss over the past decades in each of the environments we studied, we also saw significant maintenance of that diversity in some contexts, and even marked increases in specific instances,” said Stephen Brush, second author for the study and Professor Emeritus of Human Ecology and former Master Adviser for International Agricultural Development at UC Davis. 

Diversity of traditional crops remains high on farms and in gardens where landraces are valued for their unique agricultural and societal uses. One third of the 139 studies of changes in traditional crop varieties reported the maintenance of this diversity over time, and almost one quarter found evidence for the appearance of new diversity. Also, crop breeders have made significant strides toward diversifying modern crop cultivars in recent decades.  

For crop diversity to continue evolving alongside pests and diseases, in response to climate change, and to meet demands for improved crops that provide both economic products and ecological services, we need to redouble support for conservation efforts in situ, or in the field, as well as ex situ” said co-author Allison Miller, Member and Principal Investigator at the Danforth Plant Science Center and Professor of Biology at Saint Louis University. 

“In reviewing global change in the crop diversity that underpins everyone’s food security and nutrition, it’s obvious that there has been major loss, but also that the tools, methods, and knowledge exist to stop its further erosion,” said Khoury. “It is a matter of priorities and resources. To go a major step further and start to reverse the diversity trend, though, is a much bigger task. It requires no less than reframing our food systems, and even the societies they nourish, as diversity-supportive processes.”

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Read the new research article: https://doi.org/10.1111/nph.17733 

New Phytologist is a peer-reviewed scientific journal, owned by the not-for-profit New Phytologist Foundation and published by Wiley. The journal publishes high quality, original research in plant science and was founded in 1902 by botanist Arthur Tansley, after whom the Tansley review series is named. 

This work was supported by USDA National Institute of Food and Agriculture (Grant 2019-67012-29733/Project Accession 1019405). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture.

The International Potato Center (CIP) is a research-for-development organization with a focus on potato, sweetpotato and Andean roots and tubers. It delivers innovative science-based solutions to enhance access to affordable nutritious food, foster inclusive sustainable business and employment growth, and drive the climate resilience of root and tuber agri-food systems. Headquartered in Lima, Peru, CIP has a research presence in more than 20 countries in Africa, Asia and Latin America. CIP is part of CGIAR, a global research partnership for a food-secure future.www.cipotato.org 

Established in 1970, San Diego Botanic Garden (SDBG) is a 37-acre urban oasis that creates, shares and applies plant wisdom with people of all backgrounds, ages and interests. The Garden works in conservation horticulture, botany, and applied plant sciences to address our biggest local and global issues—from food security and climate change to land management and home gardening. The Garden collaborates with local academics, companies and organizations to create innovative, impactful programs and initiatives; to conserve plants and habitats for the future; and to create and share new knowledge. By expanding its scientific and conservation role to address our most pressing issues and human-plant relationships, SDBG is quickly becoming a model 21st century public plant science institution. www.sdbgarden.org  

The Alliance of Bioversity International and the International Center for Tropical Agriculture (CIAT) deliver research-based solutions that harness agricultural biodiversity and sustainably transform food systems to improve people’s lives. Alliance solutions address the global crises of malnutrition, climate change, biodiversity loss, and environmental degradation. The Alliance is part of CGIAR, a global research partnership for a food-secure future. http://www.bioversityinternational.org http://www.ciat.cgiar.org  http://www.cgiar.org

The Crop Trust is the only organization whose sole mission is to ensure humanity conserves and makes available the world’s crop diversity for future food security. Founded in 2004 by the Food and Agriculture Organization of the UN (FAO) and Bioversity International on behalf of the CGIAR, The Crop Trust leads global efforts for agricultural biodiversity. It provides financial support for the key international genebanks that make the diversity of our most important food crops available to all under the International Treaty on Plant Genetic Resources for Food and Agriculture; tools and support for the efficient management of genebanks; coordination among conserving institutions to ensure that all crop diversity is protected, accessible and used; and final backup of crop seeds in the Svalbard Global Seed Vault. https://www.croptrust.org

The University of California at Davis (UC-Davis) is a public land-grant research university and one of the most prestigious public universities in the world. The institution was founded as an agricultural branch of the UC system in 1905, and the school is ranked among the top in the world for its programs in agricultural sciences and forestry, plant and animal sciences, and agricultural economics and policy research. its graduate programs for agricultural economics, biodiversity education, entomology, evolutionary biology, plant biology, soil science, agronomy and ecology are among the top 10 programs in the US for each of these fields. The school’s campus includes 2,300 acres devoted to agricultural research and teaching.

Donald Danforth Plant Science Center is an independent, not-for-profit research institute with a mission to improve the human condition through plant science. Founded in Creve Coeur, Missouri, in 1998 by William Henry Danforth, chancellor emeritus of Washington University in St. Louis, the Center was established through a $60 million gift from the Danforth Foundation, a $50 million gift from the Monsanto Fund, the donation of 40 acres of land from Monsanto, and $25 million in tax credits from the State of Missouri. The Center’s research, education and outreach aim to have an impact at the nexus of food security and the environment and position the St. Louis region as a world center for plant science. The Center’s work is funded through competitive grants from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, and the Bill & Melinda Gates Foundation.

Founded in 1818, Saint Louis University (SLU) is one of the nation’s oldest and most prestigious Catholic research universities. Rated among the nation’s top research universities, SLU boasts 17 graduate and undergraduate programs ranked among the top 50 in the country. The Department of Biology owns and operates the Reis Biological Field Station for research and teaching, providing unique opportunities for students to explore ecology and conservation biology. Students find additional opportunities for research and hands-on experimentation at locations throughout St. Louis, including the Saint Louis Zoo and the Missouri Botanical Garden.

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