Crop diversity or crop biodiversity is the variety and variability of crops, plants used in

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...

, including their genetic and

phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...

characteristics. It is a subset of and a specific element of agricultural biodiversity. Over the past 50 years, there has been a major decline in two components of crop diversity; genetic diversity within each crop and the number of species commonly grown. Crop diversity loss threatens global

food security Food security speaks to the availability of food in a country (or geography) and the ability of individuals within that country (geography) to access, afford, and source adequate foodstuffs. According to the United Nations' Committee on World ...

, as the world's human population depends on a diminishing number of varieties of a diminishing number of crop species. Crops are increasingly grown in

monoculture In agriculture, monoculture is the practice of growing one crop species in a field at a time. Monoculture is widely used in intensive farming and in organic farming: both a 1,000-hectare/acre cornfield and a 10-ha/acre field of organic kale are ...

, meaning that if, as in the historic Great Famine of Ireland, a single disease overcomes a variety's resistance, it may destroy an entire harvest, or as in the case of the '

Gros Michel Gros Michel (), often translated and known as "Big Mike", is an export cultivar of banana and was, until the 1950s, the main variety grown. The physical properties of the Gros Michel make it an excellent export produce; its thick peel makes it re ...

' banana, may cause the commercial extinction of an entire variety. With the help of

seed bank A seed bank (also seed banks or seeds bank) stores seeds to preserve genetic diversity; hence it is a type of gene bank. There are many reasons to store seeds. One is to preserve the genes that plant breeders need to increase yield, disease res ...

s, international organizations are working to preserve crop diversity.

Biodiversity loss

The

loss of biodiversity Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...

is considered one of today’s most serious environmental concerns by the

Food and Agriculture Organization The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...

.United Nations. World Summit on Sustainable Development. August 29, 2002 If current trends persist, as many as half of all plant species could face

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

.Associated Press. "Threat seen to half of Earth's plant species". The Milwaukee Journal Sentinel (Milwaukee, WI). November 1, 2002 Some 6% of wild relatives of cereal crops such as wheat, maize, rice, and sorghum are under threat, as are 18% of legumes ( Fabaceae), the wild relatives of

beans A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes thr ...

peas The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...

and

lentils The lentil (''Lens culinaris'' or ''Lens esculenta'') is an edible legume. It is an annual plant known for its lens-shaped seeds. It is about tall, and the seeds grow in pods, usually with two seeds in each. As a food crop, the largest produ ...

, and 13% of species within the botanical family ( Solanaceae) that includes

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...

, eggplant (aubergine), and

peppers Pepper or peppers may refer to: Food and spice * Piperaceae or the pepper family, a large family of flowering plant ** Black pepper * ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanaceae ** Bell pepper ** Chili ...

(''Capsicum'').

Within-crop diversity

Fotg cocoa d066 trinidadian mixed crop cultivation of cacao

Within-crop diversity, a specific crop can result from various growing conditions, for example a crop growing in nutrient-poor soil is likely to have stunted growth than a crop growing in more fertile soil. The availability of water, soil pH level, and temperature similarly influence crop growth. Corncobs edit1

In addition, diversity of a harvested plant can be the result of genetic differences: a crop may have genes conferring early maturity or disease resistance. Such traits collectively determine a crop's overall characteristics and their future potential. Diversity within a crop includes genetically-influenced attributes such as seed size, branching pattern, height, flower color, fruiting time, and flavor. Crops can also vary in less obvious characteristics such as their response to heat, cold, a drought, or their ability to resist specific diseases and pests. Modern plant breeders develop new crop varieties to meet specific conditions. A new variety might, for example, be higher yielding, more disease resistant or have a longer shelf life than the varieties from which it was bred. The practical use of crop diversity goes back to early agricultural methods of

crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...

and

fallow Fallow is a farming technique in which arable land is left without sowing for one or more vegetative cycles. The goal of fallowing is to allow the land to recover and store organic matter while retaining moisture and disrupting pest life cycl ...

fields, where planting and harvesting one type of crop on a plot of land one year, and planting a different crop on that same plot the next year. This takes advantage of differences in a plant's nutrient needs, but more importantly reduces the buildup of pathogens. Both farmers and scientists must continually draw on the irreplaceable resource of genetic diversity to ensure productive harvests. While genetic variability provides farmers with plants that have a higher resilience to pests and diseases and allows scientists access to a more diverse genome than can be found in highly selected crops. The breeding of high performing crops steadily reduces genetic diversity as desirable traits are selected, and undesirable traits are removed. Farmers can increase within-crop diversity to some extent by planting mixtures of crop varieties.

Ecological effects

Agricultural

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s function effectively as self-regulating systems provided they have sufficient biodiversity of plants and animals. Apart from producing food, fuel, and fibre, agroecosystem functions include recycling nutrients, maintaining soil fertility, regulating

microclimate A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...

, regulating water flow, controlling pests, and

detoxification Detoxification or detoxication (detox for short) is the physiological or medicinal removal of toxic substances from a living organism, including the human body, which is mainly carried out by the liver. Additionally, it can refer to the period of ...

of waste products. However, modern agriculture seriously reduces biodiversity. Traditional systems maintain diversity within a crop species, such as in the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

mountains where up to 50 varieties of potato are grown. Strategies to raise genetic diversity can involve planting mixtures of crop varieties. Genetic diversity of crops can be used to help protect the environment. Crop varieties that are resistant to pests and diseases can reduce the need for application of harmful pesticides.Kropff, M.J. "Project: Enhanced biodiversity and weed suppression in agro-ecosystems". Crop and Weed Ecology Group (WUR), METIS Wageningen University (2001-2005)

Economic impact

Agriculture is the economic foundation of most countries, and for developing countries a likely source of economic growth. Growth in agriculture can benefit the rural poor, though it does not always do so. Profits from crops can increase from higher value crops, better marketing, value-adding activities such as processing, or expanded access for the public to markets. Profits can also decrease through reduced demand or increased production. Crop diversity can protect against

crop failure Harvesting is the process of gathering a ripe crop from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper. On smaller farms with minimal mechanization, harvesting is the most labor- ...

, and can also offer higher returns. Despite efforts to quantify them, the financial values of crop diversity sources remain entirely uncertain.

Disease threats

Along with insect pests, disease is a major cause of crop loss. Wild species have a range of

genetic variability Genetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype, or the presence of genotypically different individuals, in contrast to environmentally i ...

that allows some individuals to survive should a disturbance occur. In agriculture, resistance through variability is compromised, since genetically uniform seeds are planted under uniform conditions. Monocultural agriculture thus causes low crop diversity, especially when the seeds are mass-produced or when plants (such as grafted fruit trees and banana plants) are cloned. A single pest or disease could threaten a whole crop due to this uniformity ("

genetic erosion Genetic erosion (also known as genetic depletion) is a process where the limited gene pool of an endangered species diminishes even more when reproductive individuals die off before reproducing with others in their endangered low population. The ...

"). A well-known historic case was the Great Famine of Ireland of 1845-1847, where a vital crop with low diversity was destroyed by a single fungus. Another example is when a disease caused by a fungus affected the monocultured 1970 US corn crop, causing a loss of over one billion dollars in production. A danger to agriculture is wheat rust, a pathogenic fungus causing reddish patches, coloured by its spores. A virulent form of the wheat disease,

stem rust Stem rust, also known as cereal rust, black rust, red rust or red dust, is caused by the fungus ''Puccinia graminis'', which causes significant disease in cereal crops. Crop species that are affected by the disease include bread wheat, durum w ...

, strain Ug99, spread from

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

across to the Arabian Peninsula by 2007. In field trials in

Kenya ) , national_anthem = " Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi ...

, more than 85% of wheat samples, including major cultivars, were susceptible, implying that higher crop diversity was required. The Nobel laureate

Norman Borlaug Norman Ernest Borlaug (; March 25, 1914September 12, 2009) was an American agronomist who led initiatives worldwide that contributed to the extensive increases in agricultural production termed the Green Revolution. Borlaug was awarded multiple ...

argued for action to ensure global food security. K7725-1-sm

Reports from Burundi and

Angola , national_anthem = " Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordina ...

warn of a threat to food security caused by the African Cassava Mosaic Virus (ACMD). ACMD is responsible for the loss of a million tons of cassava each year. CMD is prevalent in all the main cassava-growing areas in the Great Lakes region of east Africa, causing between 20 and 90 percent crop losses in the Congo. The FAO emergency relief and rehabilitation program is assisting vulnerable returnee populations in the

African Great Lakes The African Great Lakes ( sw, Maziwa Makuu; rw, Ibiyaga bigari) are a series of lakes constituting the part of the Rift Valley lakes in and around the East African Rift. They include Lake Victoria, the second-largest fresh water lake in th ...

Region through mass propagation and distribution of CMD resistant or highly tolerant cassava. A well known occurrence of disease susceptibility in crops lacking diversity concerns the '

', a seedless banana that saw world marketing in the 1940s. As the market demand became high for this particular cultivar, growers and farmers began to use the Gros Michel banana almost exclusively. Genetically, these bananas are

clones Clone or Clones or Cloning or Cloned or The Clone may refer to: Places * Clones, County Fermanagh * Clones, County Monaghan, a town in Ireland Biology * Clone (B-cell), a lymphocyte clone, the massive presence of which may indicate a pathologi ...

, and because of this lack of genetic diversity, are all susceptible to a single fungus, ''

Fusarium oxysporum ''Fusarium oxysporum'' (Schlecht as emended by Snyder and Hansen), an ascomycete fungus, comprises all the species, varieties and forms recognized by Wollenweber and Reinking within an infrageneric grouping called section Elegans. It is part of ...

'' (

Panama disease Panama disease (or Fusarium wilt) is a plant disease that infects banana plants (''Musa'' spp.). It is a wilting disease caused by the fungus ''Fusarium oxysporum'' f. sp. ''cubense'' (Foc). The pathogen is resistant to fungicides and its cont ...

); large areas of the crop were destroyed by the fungus in the 1950s. 'Gros Michel' has been replaced by the current main banana on the market, the 'Cavendish', which in turn is (2015) at risk of total loss to a strain of the same fungus, 'Tropical Race 4'. Such threats can be countered by strategies such as planting multi-line cultivars and cultivar mixes, in the hope that some of the cultivars will be resistant to any individual outbreak of disease.

Organizations and technologies

The implications of crop diversity are at both local and world levels. Global organizations that aim to support diversity include Bioversity International (formerly known as International Plant Genetic Resources Institute), the

International Institute of Tropical Agriculture The International Institute of Tropical Agriculture (IITA) is a nonprofit organization that works with partners to enhance crop quality and productivity, reduce producer and consumer risks, and generate wealth from agriculture, with the ultimate ...

, the

Borlaug Global Rust Initiative The Borlaug Global Rust Initiative (BGRI - originally named the Global Rust Initiative) was founded in response to recommendations of a committee of international experts who met to consider a response to the threat the global food supply posed by t ...

, and the International Network for Improvement of Banana and Plantain. Members of the United Nations, at the World Summit on Sustainable Development 2002 at Johannesburg, said that crop diversity is in danger of being lost if measures are not taken. One such step taken in the action against the loss of biodiversity among crops is gene banking. There are a number of organizations that enlist teams of local farmers to grow native varieties, particularly those that are threatened by extinction due to lack of modern-day use. There are also local, national and international efforts to preserve agricultural genetic resources through off-site methods such as seed and banks for further research and crop breeding. Six bean varieties at a gene bank

The

Global Crop Diversity Trust The Crop Trust, officially known as the Global Crop Diversity Trust, is an international nonprofit organization with a secretariat in Bonn, Germany. Its mission is to conserve and make available the world's crop diversity for food security. Esta ...

is an independent

international organisation An international organization or international organisation (see spelling differences), also known as an intergovernmental organization or an international institution, is a stable set of norms and rules meant to govern the behavior of states an ...

which exists to ensure the

conservation Conservation is the preservation or efficient use of resources, or the conservation of various quantities under physical laws. Conservation may also refer to: Environment and natural resources * Nature conservation, the protection and managem ...

and availability of crop diversity for food security worldwide. It was established through a partnership between the

United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmoniz ...

(FAO) and

CGIAR CGIAR (formerly the Consultative Group for International Agricultural Research) is a global partnership that unites international organizations engaged in research about food security. CGIAR research aims to reduce rural poverty, increase food ...

acting through Bioversity International. The CGIAR is a consortium of international agriculture research centers (IARC) and others that each conduct research on and preserve germplasm from a particular crop or animal species. The genebanks of CGIAR centers hold some of the world's largest off site collections of plant genetic resources in trust for the world community. Collectively, the CGIAR genebanks contain more that 778,000 accessions of more than 3,000 crop, forage, and agroforestry species. The collection includes farmers' varieties and improved varieties and, in substantial measure, the wild species from which those varieties were created. National germplasm storage centers include the

U.S. Department of Agriculture The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of comme ...

's National Center for Genetic Resources Preservation, India's National Bureau of Animal Genetic Resources, the

Taiwan Livestock Research Institute The Taiwan Livestock Research Institute (TLRI; ) is a research center in Xinhua District, Tainan, Taiwan. It conducts research on animal breeding, physiology, nutrition and feeding techniques, animal waste treatment and utilization of byprod ...

, and the proposed Australian Network of Plant Genetic Resource Centers. Genebank4 (4331057760)

The

World Resources Institute The World Resources Institute (WRI) is a global research non-profit organization established in 1982 with funding from the MacArthur Foundation under the leadership of James Gustave Speth. WRI's activities are focused on seven areas: food, for ...

(WRI) and the

World Conservation Union The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN) are non-profit organizations that provide funding and other support to off site and on site conservation efforts. The wise use of crop genetic diversity in plant breeding and genetic modification can also contribute significantly to protecting the biodiversity in crops. Crop varieties can be genetically modified to resist specific pests and diseases. For example, a gene from the soil

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

'' Bacillus thuringiensis'' (Bt) produces a natural insecticide

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

. Genes from Bt can be inserted into crop plants to make them capable of producing an insecticidal toxin and therefore a resistance to certain pests. Bt corn (

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...

) can however adversely affect non-target insects closely related to the target pest, as with the monarch butterfly.

Notes

References

External links

Diverseeds videos on crop diversity

Diverseeds documentary film on the global importance of plant genetic resources for food security

Seeds of Survival, a project of USC Canada

One seed at a time, protecting the future of food TED talk
{{Agriculture footer Crops Sustainable agriculture Biodiversity Agronomy