Information

12.2B: Agricultural Diversity - Biology


Maintaining genetic biodiversity of wild species of our crops that are related to domesticated species ensures our continued food supply.

Learning Objectives

  • Assess the interactions of biodiversity with agricultural diversity

Key Points

  • Agricultural diversity is driven by the demands of the topography, the limited movement of people, and the needs for crop rotation of varieties that do well in different fields.
  • Resistance to disease is a chief benefit to maintaining crop biodiversity; lack of diversity in crop species risks an entire crop being wiped out by a disease to which it is susceptible.
  • The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant that can be bred with existing varieties.
  • Seed companies must continually breed new varieties to keep up with evolving pest organisms.

Key Terms

  • blight: any of many plant diseases causing damage to, or the death of, leaves, fruit or other parts

Agricultural Diversity

Since the beginning of human agriculture more than 10,000 years ago, human groups have been breeding and selecting crop varieties. This crop diversity matched the cultural diversity of highly-subdivided populations of humans. For example, potatoes were domesticated beginning around 7,000 years ago in the central Andes of Peru and Bolivia. The potatoes grown in that region belong to seven species, while the number of varieties is probably in the thousands. Each variety has been bred to thrive at particular elevations and soil and climate conditions. The diversity is driven by the demands of the topography, the limited movement of people, and the demands created by crop rotation for different varieties that will do well in different fields and microclimates.

Potatoes are only one example of human-generated diversity. Every plant, animal, and fungus that has been cultivated by humans has been bred from original wild ancestor species into diverse varieties arising from the demands for food value, adaptation to growing conditions, and resistance to pests. The potato demonstrates a well-known example of the risks of low crop diversity. The tragic, Irish potato famine occurred when the single variety grown in Ireland became susceptible to a potato blight, wiping out the crop. The loss of the crop led to famine, death, and mass emigration. Resistance to disease is a chief benefit to maintaining crop biodiversity; lack of diversity in contemporary crop species carries similar risks. Seed companies, which are the source of most crop varieties in developed countries, must continually breed new varieties to keep up with evolving pest organisms. These same seed companies, however, have participated in the decline of the number of varieties available as they focus on selling fewer varieties in more areas of the world.

The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant. These wild forms are often the source of new gene variants that can be bred with existing varieties to create varieties with new attributes. Loss of wild species related to a crop will mean the loss of potential in crop improvement. Maintaining the genetic diversity of wild species related to domesticated species ensures our continued food supply.

Since the 1920s, government agriculture departments have maintained seed banks of crop varieties as a way to maintain crop diversity. Sometimes, however, seed banks are lost through accidents; there is no way to replace them. In 2008, the Svalbard Global Seed Vault began storing seeds from around the world as a backup system to the regional seed banks. If a regional seed bank stores varieties in Svalbard, losses can be replaced from those stored here. The seed vault is located deep into the rock of an arctic island. Conditions within the vault are maintained at ideal temperature and humidity for seed survival, but the deep underground location of the vault in the arctic means that failure of the vault’s systems will not compromise the climatic conditions inside the vault.


Richard Lewontin

Richard Charles "Dick" Lewontin (born March 29, 1929) is an American evolutionary biologist, mathematician, geneticist, and social commentator. A leader in developing the mathematical basis of population genetics and evolutionary theory, he pioneered the application of techniques from molecular biology, such as gel electrophoresis, to questions of genetic variation and evolution.

In a pair of seminal 1966 papers co-authored with J.L. Hubby in the journal Genetics, [3] [4] Lewontin helped set the stage for the modern field of molecular evolution. In 1979 he and Stephen Jay Gould introduced the term "spandrel" into evolutionary theory. From 1973 to 1998, he held an endowed chair in zoology and biology at Harvard University, and since 2003 has been a research professor there.


Agricultural Diversity

Since the beginning of human agriculture more than 10,000 years ago, human groups have been breeding and selecting crop varieties. This crop diversity matched the cultural diversity of highly subdivided populations of humans. For example, potatoes were domesticated beginning around 7,000 years ago in the central Andes of Peru and Bolivia. The potatoes grown in that region belong to seven species and the number of varieties likely is in the thousands. Each variety has been bred to thrive at particular elevations and soil and climate conditions. The diversity is driven by the diverse demands of the topography, the limited movement of people, and the demands created by crop rotation for different varieties that will do well in different fields.

Potatoes are only one example of human-generated diversity. Every plant, animal, and fungus that has been cultivated by humans has been bred from original wild ancestor species into diverse varieties arising from the demands for food value, adaptation to growing conditions, and resistance to pests. The potato demonstrates a well-known example of the risks of low crop diversity: the tragic Irish potato famine when the single variety grown in Ireland became susceptible to a potato blight, wiping out the crop. The loss of the crop led to famine, death, and mass emigration. Resistance to disease is a chief benefit to maintaining crop biodiversity, and lack of diversity in contemporary crop species carries similar risks. Seed companies, which are the source of most crop varieties in developed countries, must continually breed new varieties to keep up with evolving pest organisms. These same seed companies, however, have participated in the decline of the number of varieties available as they focus on selling fewer varieties in more areas of the world.

The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant. These wild forms are often the source of new gene variants that can be bred with existing varieties to create varieties with new attributes. Loss of wild species related to a crop will mean the loss of potential in crop improvement. Maintaining the genetic diversity of wild species related to domesticated species ensures our continued food supply.

Since the 1920s, government agriculture departments have maintained seed banks of crop varieties as a way to maintain crop diversity. This system has flaws because, over time, seed banks are lost through accidents, and there is no way to replace them. In 2008, the Svalbard Global Seed Vault (see the figure below) began storing seeds from around the world as a backup system to the regional seed banks. If a regional seed bank stores varieties in Svalbard, losses can be replaced from Svalbard. The seed vault is located deep into the rock of an arctic island. Conditions within the vault are maintained at ideal temperature and humidity for seed survival, but the deep underground location of the vault in the arctic means that failure of the vault’s systems will not compromise the climatic conditions inside the vault.

Art Connection

The Svalbard Global Seed Vault is a storage facility for seeds of Earth’s diverse crops. (credit: Mari Tefre, Svalbard Global Seed Vault)

The Svalbard Global Seed Vault is located on Spitsbergen island in Norway, which has an arctic climate. Why might an arctic climate be good for seed storage?

Crop success s is largely dependent on the quality of the soil. Although some agricultural soils are rendered sterile using controversial cultivation and chemical treatments, most contain a huge diversity of organisms that maintain nutrient cycles—breaking down organic matter into nutrient compounds that crops need for growth. These organisms also maintain soil texture that affects water and oxygen dynamics in the soil that are necessary for plant growth. If farmers had to maintain arable soil using alternate means, the cost of food would be much higher than it is now. These kinds of processes are called ecosystem services. They occur within ecosystems, such as soil ecosystems, as a result of the diverse metabolic activities of the organisms living there, but they provide benefits to human food production, drinking water availability, and breathable air.

Other key ecosystem services related to food production are plant pollination and crop pest control. Over 150 crops in the United States require pollination to produce. One estimate of the benefit of honeybee pollination within the United States is $1.6 billion per year other pollinators contribute up to $6.7 billion more.

Many honeybee populations are managed by apiarists who rent out their hives’ services to farmers. Honeybee populations in North America have been suffering large losses caused by a syndrome known as colony collapse disorder, whose cause is unclear. Other pollinators include a diverse array of other bee species and various insects and birds. Loss of these species would make growing crops requiring pollination impossible, increasing dependence on other crops.

Finally, humans compete for their food with crop pests, most of which are insects. Pesticides control these competitors however, pesticides are costly and lose their effectiveness over time as pest populations adapt. They also lead to collateral damage by killing non-pest species and risking the health of consumers and agricultural workers. Ecologists believe that the bulk of the work in removing pests is actually done by predators and parasites of those pests, but the impact has not been well studied. A review found that in 74 percent of studies that looked for an effect of landscape complexity on natural enemies of pests, the greater the complexity, the greater the effect of pest-suppressing organisms. An experimental study found that introducing multiple enemies of pea aphids (an important alfalfa pest) increased the yield of alfalfa significantly. This study shows the importance of landscape diversity via the question of whether a diversity of pests is more effective at control than one single pest the results showed this to be the case. Loss of diversity in pest enemies will inevitably make it more difficult and costly to grow food.


Recent collapse of crop belts and declining diversity of US agriculture since 1840

Michael S. Crossley, 120 Cedar St., 413 Biological Sciences Bldg., Athens, GA 30602, USA.

Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, WI, USA

Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA

SILVIS Lab, Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA

Department of Entomology, University of Georgia, Athens, GA, USA

Michael S. Crossley, 120 Cedar St., 413 Biological Sciences Bldg., Athens, GA 30602, USA.

Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, WI, USA

Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA

SILVIS Lab, Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA

Abstract

Over the last century, US agriculture greatly intensified and became industrialized, increasing in inputs and yields while decreasing in total cropland area. In the industrial sector, spatial agglomeration effects are typical, but such changes in the patterns of crop types and diversity would have major implications for the resilience of food systems to global change. Here, we investigate the extent to which agricultural industrialization in the United States was accompanied by agglomeration of crop types, not just overall cropland area, as well as declines in crop diversity. Based on county-level analyses of individual crop land cover area in the conterminous United States from 1840 to 2017, we found a strong and abrupt spatial concentration of most crop types in very recent years. For 13 of the 18 major crops, the widespread belts that characterized early 20th century US agriculture have collapsed, with spatial concentration increasing 15-fold after 2002. The number of counties producing each crop declined from 1940 to 2017 by up to 97%, and their total area declined by up to 98%, despite increasing total production. Concomitantly, the diversity of crop types within counties plummeted: in 1940, 88% of counties grew >10 crops, but only 2% did so in 2017, and combinations of crop types that once characterized entire agricultural regions are lost. Importantly, declining crop diversity with increasing cropland area is a recent phenomenon, suggesting that corresponding environmental effects in agriculturally dominated counties have fundamentally changed. For example, the spatial concentration of agriculture has important consequences for the spread of crop pests, agrochemical use, and climate change. Ultimately, the recent collapse of most agricultural belts and the loss of crop diversity suggest greater vulnerability of US food systems to environmental and economic change, but the spatial concentration of agriculture may also offer environmental benefits in areas that are no longer farmed.


C. P. Gillette Museum of Arthropod Diversity

The C. P. Gillette Museum of Arthropod Diversity houses more than three and a half million specimens and has excellent representation of most orders of insects especially with a strong in the coverage of Rocky Mountain species, but also southwestern species. The collection houses holdings of national importance in the aquatic insect orders, the Lepidoptera (butterflies and moths), the Diptera (flies, gnats and mosquitos), and the Hymenoptera (ants, bees, wasps and relatives. The Collection houses 83 primary types and more than 2,000 secondary types (Baker, Evans, Gillette, James, Fisher, Kondratieff, Opler, Palmer and others). The associated Bruner Family Library contains important systematic literature. Research, undergraduate and graduate training, and outreach activities are prominent among museum-related activities.

Dr. Clarence P. Gillette, an entomologist of international reputation, established an insect collection in the late 1800s to assist the College of Agricultural Sciences in fulfilling its missions in teaching, research, and extension. Throughout its history, the C. P. Gillette Museum of Arthropod Diversity (CSUC) has been available for research and scholarship with minimal restrictions to students, faculty, visiting scientists (including international researchers), the general public, and other interested people. Gillette expanded and curated the CSUC from 1891 to about 1930. Since that time, the internationally recognized entomologists, George List, T. O. Thatcher, Howard E. Evans, Paul A. Opler, Don Bright, and Don Givens have continued enhancing and expanding the collection. B. C. Kondratieff has served as director of the CSUC since 1986. Currently, the CSUC includes more than three and a half million specimens and is considered the fourteenth largest institutional insect collections in the United States. The Collection belongs to the Department of Agricultural Biology, Colorado State University. The Department (Dr. Amy Charkowski, Head) is administered through the College of Agricultural Sciences and Colorado.

The CSUC includes more than three and a half million specimens, with extensive coverage of the southern Rocky Mountain Region, in addition to excellent representation of many North American taxa (Table 1). Approximately 5% of the CSUC includes material collected from outside North America, primarily from Mexico and selected Central and South American countries. Presently, it is considered to be the fourteenth largest insect collection affiliated with a U.S.A. university in the U.S. Much of the material has been identified by specialists to the genus or species level, making it very valuable in terms of quality of material.

Currently housed in the CSUC is an extensive taxonomic research library of essential books and publications (The Bruner Family Library). The library includes approximately 1,200 books and 12,000 bulletins, reprints and other literature items that deal with arthropod systematics. Primary literature and catalogs are available for most groups of North American insects with special holdings of world aphid literature. The CSUC produces a scientific publication series: “Contributions of the C. P. Gillette Museum of Arthropod Diversity.” Titles are available on the CSU Department of Agricultural Biology website. Most titles are available online as open access by the CSU digital library of the Morgan Library.

The CSUC is now located at 600 Hughes Way. (The old Hartshorn Health Center).


Importance of Genetic Diversity in Agriculture

World Vegetable Center houses the largest public collection of vegetable germplasm in the world. Germplasm are living genetic resources such as seeds or tissue that are maintained for their use in plant breeding. The collection safeguards vegetable crop genetic diversity that may be useful in the future. Jack Harlan, an agronomist and botanist once said, regarding the biodiversity within crop species (genetic diversity), “stands between us and catastrophic starvation on a scale we cannot imagine.” According to the United Nations Food and Agriculture Organization, 75% of all crop genetic diversity has been lost since the previous century, primarily due to changes in the agricultural food system which values uniformity. Of the remaining 25%, one third is expected to become extinct by 2050. Genetic diversity is the total number of genetic characteristics in the genome of a species. Curators of crop genetic diversity include seed banks, gene banks and agricultural research institutions that house collections of seeds and propagative material. These collections house the world’s tools to cope with new challenges within our food system. Agricultural genetic diversity is imperative to provide a robust food security system capable of adapting to pest and environmental stressors. Genetic diversity allows agricultural plant and animal breeders to adapt to changing variables.

According to the International Development Research Center, the global food supply “depends on about 150 plant species. Of those, just 12 provide three-quarters of the world’s food. More than half of the world’s food energy comes from a limited number of varieties of three “mega-crops”: rice, wheat, and maize”. The global food supply is increasingly under threat from climate change, world population growth and the introduction or range expansion of disease and insects. Genetic diversity is needed to safeguard potentially vital traits that could be used to combat an unexpected future pest or adapt to the needs of the world’s food supply. Plant breeders utilize genetic diversity to create improved crop varieties with traits such as yield, pest resistance and environment stress.

To adequately store genetic diversity, it is important the germplasm collections are well maintained, and backup collections are created to ensure its survival in case of a natural disaster or political unrest. Seeds and plant tissues are stored in-situ, meaning stored in a controlled environment such as cold storage or tissue culture facility. In-situ storage requires a relatively small space to accommodate a large amount of material. While propagative material from plants such as trees, shrubs and clonally propagated crops are stored ex-situ, meaning crops are preserved in an outside environment. Ex-situ storage requires a lot of space and are vulnerable to pests, natural disasters and human nature. These crops are the most at risk for extinction and most collections remain largely unstudied.

There are partnerships with private and governmental seed bank institutions to preserve crops that can be stored in-situ for long periods of time in the form of seeds at the Svalbard Global Seed Bank located north of the Arctic Circle. The Svalbard Global Seed Bank acts as a safety deposit box which allows institutions to safety deposit and withdraw their backup seed collections in case their main collection is lost or severely damaged. There are some regional and national partnerships regarding ex-situ crops in the United States and abroad, but international partnerships are difficult to conduct due to plant quarantine restrictions and the possible importation of pests. Until new efficient methods are devised to limit the transfer of pests, there is a need for increased funding and effort to create more backup collection sites spread throughout the world. It is important that the remaining uncollected crop genetic diversity from wild crop relatives, unique plant populations with low representation in gene banks and minor crops located in remote regions of the world, are collected and preserved before they go extinct. Wild crop relatives are the ancestors of our domesticated crops. They may contain important genetic traits, which may have been lost during the domestication process. Traits such as drought or pest resistance will be crucial in adapting to climate change. Many wild crop species are at risk for extinction due to habitat destruction or the encroachment of urban sprawl. Unique plant populations that are currently underrepresented in gene banks need to be collected due to current material limited to a few individuals, which does not adequately represent all the genetic diversity within that population. These populations are located in small pockets, which are extremely vulnerable to extinction due to pests or human activity.

The United States Plant Germplasm System currently houses almost 580,000 accessions of crop material. In the last 8 years it has gained almost 60,000 more accessions. An accession is an individual cultivar or variety of a crop. During the same period, the budget has remained relatively stagnant. With such a large increase in the amount of accessions being curated, resources devoted to important programs such as plant expeditions, infrastructure, regeneration, and development of improved conservation practices are strained. Genetic diversity is an important resource that needs to be properly collected and conserved for future generations.

Genetic diversity will play a crucial role in the development of crops adapted to climate change and the production of food for the growing world population. To ensure these resources are available to plant breeders in the future, more public funding in seed banks and agricultural institutions is needed. The public needs to be informed of the importance of our genetic resources for the sake of improving the global food system.


News and Events from the Penn State College of Agricultural Sciences

Four honored for commitment to diversity in College of Agricultural Sciences

Four individuals have received the 2021 Dr. William Henson Diversity Achievement Award from Penn State's College of Agricultural Sciences, an honor that recognizes distinctive and outstanding teaching, research, extension or creative work that advances diversity in the college.

Novel study looks at nitrogen credit trading to spur growth of riparian buffers

Watershedwide nutrient credit trading has been suggested as a mechanism for reducing pollution entering the Chesapeake Bay, but a new study by Penn State researchers suggests that the high cost of producing nitrogen credits through the establishment of riparian buffers on Pennsylvania farmland currently does not provide an incentive for buffer establishment.


Effect of Widespread Agricultural Chemical Use on Butterfly Diversity across Turkish Provinces

Institute for Conservation Research, San Diego Zoo Global, 15600 San Pasqual Valley Road, Escondido, CA, 92027 U.S.A.

Institute for Conservation Research, San Diego Zoo Global, 15600 San Pasqual Valley Road, Escondido, CA, 92027 U.S.A.

Abstract

Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land-cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertilizers and pesticides. I used constrained correspondence analyses and regression-based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combination of agricultural chemical use, particularly pesticides, and climatic and land-cover variables. Although overall butterfly richness was primarily explained by climatic and land-cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low-input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey.

Efectos del Uso Extensivo de Agroquímicos sobre la Diversidad de Mariposas en Provincias Turcas

Resumen

Aunque se piensa que la intensificación agrícola representa una amenaza significativa para las especies, se sabe poco sobre su papel en la pérdida de biodiversidad en escalas regionales. Evalué los efectos de un componente principal de la intensificación agrícola, el uso de agroquímicos, la cobertura de suelo y variables climáticas sobre la diversidad de mariposas en 81 provincias de Turquía, donde la agricultura se practica extensivamente pero con diferentes niveles de intensidad. Determiné la presencia de especies de mariposas en cada provincia a partir de datos de las distribuciones conocidas y medí el uso de agroquímicos como la proporción de agricultores que utilizan fertilizantes y pesticidas químicos. Utilicé análisis de correspondencia constreñida e inferencia con multimodelos basados en regresiones para determinar el efecto de las variables ambientales sobre la composición y riqueza de especies, respectivamente. La variación en la composición de especies de mariposas en las provincias fue explicada principalmente (86%) por la combinación del uso de agroquímicos, particularmente pesticidas, y las variables climáticas y de cobertura de suelo. Aunque la riqueza total de mariposas fue explicada primariamente por variables climáticas y de cobertura de suelo, como la superficie de cubierta vegetal natural, la riqueza de mariposas amenazadas y el número relativo de especies de mariposas amenazadas disminuyó sustancialmente a medida que incrementó la proporción de agricultores que utilizan pesticidas. Estos resultados sugieren que el uso extensivo de agroquímicos, u otros componentes de la intensificación agrícola que pueden utilizados con pesticidas, representan una amenaza para la biodiversidad de Turquía. En consecuencia, las políticas que mitigan la intensificación agrícola y promueven las prácticas agrícolas de bajo insumo son cruciales para la protección de especies amenazadas en países con industrialización acelerada como Turquía.


The importance of agricultural lands for Himalayan birds in winter

Woodrow Wilson School, Princeton University, Princeton, NJ, 08544 U.S.A.

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544 U.S.A.

Current address: Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA 94720, U.S.A. email [email protected] Search for more papers by this author

Himal Prakriti, Village Sarmoli, Munsiari, Pithoragarh, Uttarakhand, 262554 India

Wildlife Institute of India, Dehradun, Uttarakhand, 248001 India

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544 U.S.A.

Woodrow Wilson School, Princeton University, Princeton, NJ, 08544 U.S.A.

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544 U.S.A.

Current address: Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA 94720, U.S.A. email [email protected] Search for more papers by this author

Himal Prakriti, Village Sarmoli, Munsiari, Pithoragarh, Uttarakhand, 262554 India

Wildlife Institute of India, Dehradun, Uttarakhand, 248001 India

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544 U.S.A.

Abstract

The impacts of land-use change on biodiversity in the Himalayas are poorly known, notwithstanding widespread deforestation and agricultural intensification in this highly biodiverse region. Although intact primary forests harbor many Himalayan birds during breeding, a large number of bird species use agricultural lands during winter. We assessed how Himalayan bird species richness, abundance, and composition during winter are affected by forest loss stemming from agriculture and grazing. Bird surveys along 12 elevational transects within primary forest, low-intensity agriculture, mixed subsistence agriculture, and intensively grazed pastures in winter revealed that bird species richness and abundance were greatest in low-intensity and mixed agriculture, intermediate in grazed pastures, and lowest in primary forest at both local and landscape scales over twice as many species and individuals were recorded in low-intensity agriculture than in primary forest. Bird communities in primary forests were distinct from those in all other land-use classes, but only 4 species were unique to primary forests. Low-, medium-, and high-intensity agriculture harbored 32 unique species. Of the species observed in primary forest, 80% had equal or greater abundance in low-intensity agricultural lands, underscoring the value of these lands in retaining diverse community assemblages at high densities in winter. Among disturbed landscapes, bird species richness and abundance declined as land-use intensity increased, especially in high-intensity pastures. Our results suggest that agricultural landscapes are important for most Himalayan bird species in winter. But agricultural intensification—especially increased grazing—will likely result in biodiversity losses. Given that forest reserves alone may inadequately conserve Himalayan birds in winter, comprehensive conservation strategies in the region must go beyond protecting intact primary forests and ensure that low-intensity agricultural lands are not extensively converted to high-intensity pastures.

Abstract

La Importancia de las Tierras Agrícolas para las Aves del Himalaya en el Invierno

Resumen

Los impactos del cambio de uso de suelo sobre la biodiversidad en el Himalaya son poco conocidos, a pesar de la deforestación extendida y la intensificación agrícola en esta región altamente biodiversa. Aunque los bosques primarios intactos albergan a muchas aves del Himalaya durante la época reproductiva, un gran número de especies de aves utilizan las tierras agrícolas durante el invierno. Valoramos cómo la riqueza, abundancia y composición de especies de aves del Himalaya durante el invierno son afectadas por la pérdida del bosque a partir de la agricultura y el pastoreo. Los censos de aves a lo largo de doce transectos de altitud dentro del bosque primario, de la agricultura de baja intensidad, de la agricultura de subsistencia mixta y de las zonas de pastoreo intensivo en invierno revelaron que la riqueza de especies de aves y la abundancia fueron mayores en la agricultura de baja intensidad y en la mixta, intermedias en las zonas de pastoreo, y más bajas en el bosque primario tanto en la escala local como la de paisaje más del doble de especies y de individuos se registraron en la agricultura de baja intensidad que en el bosque primario. Las comunidades de aves en el bosque primario fueron distintas de aquellas en todos los demás tipos de uso de suelo, pero sólo cuatro especies fueron únicas de los bosques primarios. La agricultura de intensidad baja, media y alta albergó 32 especies únicas. De las especies observadas en el bosque primario, el 80 % tuvo una abundancia igual o mayor en los suelos de baja intensidad agrícola, enfatizando el valor de estos suelos en la retención de ensamblajes diversos de comunidades a densidades altas durante el invierno. Entre los paisajes perturbados, la riqueza de especies y la abundancia declinaron conforme incrementó la intensidad del uso de suelo, especialmente en las pasturas de alta intensidad. Nuestros resultados sugieren que los paisajes agrícolas son importantes para la mayoría de las especies de aves del Himalaya durante el inverno aunque la intensificación agrícola – especialmente el pastoreo incrementado – probablemente resultará en la pérdida de la biodiversidad. Dado que las reservas de bosques por sí solas pueden conservar inadecuadamente a las aves del Himalaya en inverno, las estrategias integrales de conservación en la región deben ir más allá de proteger los bosques primarios intactos y asegurar que los suelos de uso agrícola de baja intensidad no sean convertidos extensivamente a zonas de pastoreo de alta intensidad.


Lack of crop diversity and increasing dependence on pollinators may threaten food security

Honey bee worker and a male Andrena sp on apple blossom. Credit: Martin Husemann

A multinational team of researchers has identified countries where agriculture's increasing dependence on pollination, coupled with a lack of crop diversity, may threaten food security and economic stability. The study, which was published in the journal Global Change Biology on July 11, 2019, is the first global assessment of the relationship between trends in crop diversity and agricultural dependence on pollinators.

Using annual data from the U.N. Food and Agriculture Organization from 1961 to 2016, the study showed that the global area cultivated in crops that require pollination by bees and other insects expanded by 137%, while crop diversity increased by just 20.5%. This imbalance is a problem, according to the researchers, because agriculture dominated by just one or two types of crops only provides nutrition for pollinators during a limited window when the crops are blooming. Maintaining agricultural diversity by cultivating a variety of crops that bloom at different times provides a more stable source of food and habitat for pollinators.

"This work should sound an alarm for policymakers who need to think about how they are going to protect and foster pollinator populations that can support the growing need for the services they provide to crops that require pollination," said David Inouye, professor emeritus of biology at the University of Maryland and a co-author of the research paper.

Globally, a large portion of the total agricultural expansion and increase in pollinator dependence between 1961 and 2016 resulted from increases in large-scale farming of soybean, canola and palm crops for oil. The researchers expressed concern over the increase in these crops because it indicates a rapid expansion of industrial farming, which is associated with environmentally damaging practices such as large monocultures and pesticide use that threaten pollinators and can undermine productivity.

Bumble bee on a thistle flower. Credit: David Inouye/University of Maryland

Particularly vulnerable to potential agricultural instability are Brazil, Argentina, Paraguay and Bolivia, where expansion of pollinator-dependent soybean farms has driven deforestation and replaced rich biodiversity that supports healthy populations of pollinators with large-scale single-crop agriculture (monoculture). Malaysia and Indonesia face a similar scenario from the expansion of oil palm farming.

"Farmers are growing more crops that require pollination, such as fruits, nuts and oil seeds, because there's an increasing demand for them and they have a higher market value," Inouye said. "This study points out that these current trends are not great for pollinators, and countries that diversify their agricultural crops are going to benefit more than those that expand with only a limited subset of crops."

Although the study found that countries replacing forests and diverse, heterogeneous agricultural landscapes with extensive with pollinator-dependent monoculture are most vulnerable, other countries also face risks from growing dependence on pollinators.

In Europe, farmland is contracting as development replaces agriculture, but pollinator-dependent crops are replacing non-pollinator-dependent crops such as rice and wheat (which are wind pollinated). According to the study, increasing need for pollination services without parallel increases in diversity puts agricultural stability at risk in places like Australia, the United Kingdom, Germany, France, Austria, Denmark and Finland.

Leaf cutter bee on lupine. Credit: David Inouye / University of Maryland

In the U.S., agricultural diversity has not kept pace with expansion of industrial-scale soybean farming.

"This work shows that you really need to look at this issue country by country and region by region to see what's happening because there are different underlying risks," Inouye said. "The bottom line is that if you're increasing pollinator crops, you also need to diversify crops and implement pollinator-friendly management."

Inouye said the researchers are hoping this work will spur policymakers and resource managers to reevaluate current trends and practices to introduce more pollinator-friendly management such as reducing insecticide use, planting edge rows and flower strips to provide nest sites and food for pollinators, and restoring seminatural and natural areas adjacent to crops.


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