Biological diversity, or biodiversity for short, encompasses the variety of life at all levels of organization, from genetic diversity within a species to diversity within entire regions or ecosystems. 1 Biodiversity is increasingly recognized as critical to human life, but many species are more threatened than ever by urbanization, global deforestation, climate change , overexploitation of the world’s fisheries and marine ecosystems, industrial agricultural expansion and other human activities. 3
The diversity of life on our planet is critical for maintaining the basic planetary life support systems we rely on every day. Ecosystem services, or the resources nature provides us free of charge, like drinking water, crop pollination, nutrient cycling and climate regulation, all rely on biodiversity. For instance, the diversity of insect and avian pollinators is crucial to global agricultural productivity, ensuring plants produce harvestable crops for human use.
The Earth’s staggering biodiversity is also responsible for more tangible human goods. In many parts of the world, plants are the main source of medicine used for primary health care, linking the survival of plant diversity with human well-being. 4 Additionally, many of our most important pharmaceutical drugs come from compounds discovered only in specific plants or organisms, meaning future drug discoveries may well depend on the survival of species that have yet to be studied for their medicinal properties.
Farmers rely on services provided by ecosystems to produce the foods we eat every day, and the health of ecosystems, in turn, are dependent on biodiversity. The relationship between agriculture and biodiversity can be understood in two ways—first, as the biodiversity within farmland landscapes (i.e. the biodiversity of soil microbes, birds, insects, etc.) and also as the biodiversity of agricultural crops and animals, or agrobiodiversity (i.e. breeds of cattle, varieties of wheat, etc.).
Biodiversity is important at all scales of the agricultural landscape. From billions of different soil microbes that help cycle nutrients and decompose organic matter, to wasps and bats that help reduce crop pests, to birds and insects that pollinate high value crops, biodiversity helps farmers successfully grow food and maintain sustainable farm landscapes.
For example, although many of our most important crops are wind-pollinated and do not require pollinators, 39 of the leading 57 global crops benefit from natural pollinators, such as birds and insects. 5 A striking example of our dependence on pollinator services and the damage that can be inflicted on the agricultural economy without them can be seen in the decline of US honeybee populations beginning in late 2006 which became known as Colony Collapse Disorder (CCD). Although scientific debate continues on the ultimate causes of CCD, 6 honeybee declines have served as an important wakeup call to protect both our managed and wild pollinator species.
But not only does the maintenance of biodiversity help ensure viable crop production, many organisms and species have come to rely on particular agricultural landscapes for their very survival. As an example, farmland bird biodiversity in Europe has declined dramatically in the past two decades as a result of the intensification and industrialization of Europe’s farmland and agriculture practices. 7 In sum, agriculture both supports, and is supported by, the maintenance of biodiversity.
Agrobiodiversity refers to biodiversity among planned agricultural crops or livestock, such as the genetic diversity of wheat varieties or cattle breeds. Agrobiodiversity is the result of thousands of years of human intervention in selectively breeding traits in animals and crops for particular agricultural advantages. A famous example of the diversity that can exist within one crop species is found in the diversity of potatoes grown in the Andes of South America, where potatoes originated and some 4,000 known varieties, or landraces, exist. 8 This abundance of diversity is the result of farmers artificially selecting traits over generations for specific purposes, like resistance to disease, tolerance to high altitudes or poor soils, etc. This diversity is important for food security—in the event that a particular crop variety fails due to drought, flooding or a disease, another variety might survive to avoid food shortages. In stark contrast to this model of agrobiodiversity, the Irish Potato Famine of the 1840s was the result of a fungus that completely destroyed the Irish potato crop because only a few varieties of potatoes had been imported from the Andes to Europe, none of which were resistant to the disease. Because of a lack of crop diversity and overreliance on one crop to feed many of its population, Ireland experienced widespread famine and death. 9
Diminishing agrobiodiversity is not only a historical problem, however. The FAO has estimated that during the last century, 75 percent of crop genetic diversity has been lost, a phenomenon referred to as genetic erosion. 10 This loss of genetic diversity in plant crops and animal breeds is dangerous because it makes our food supply more vulnerable to outbreaks of pests and disease. For instance, in the 1970s, a lack of genetic diversity in US corn varieties resulted in the loss of over 1 billion US dollars due to a lack of resistance to leaf blight. 10 Unfortunately, the situation has not improved today, as increasingly, industrial food production relies on fewer and fewer crop varieties and animal breeds, further imperiling the security of our food system.
As mentioned earlier, industrial agriculture can reduce biodiversity by also diminishing biodiversity in the wider agricultural landscape. Excessive manure, nutrient and pesticide runoff from industrial animal and plant agriculture can all negatively impact both aquatic and terrestrial ecosystems and the biodiversity they support. Nutrient runoff can cause eutrophication of bodies of water like rivers and streams, in some cases literally suffocating fish and other organisms, resulting in mass die-offs. Pesticide runoff has been implicated in reducing biodiversity within agricultural landscapes both within terrestrial and aquatic landscapes, a famous example being the near eradication of a number of US bird species from the use of the insecticide DDT during the second half of the 20th Century. 12
A major cause of farmland biodiversity declines in the last century is the simplification of the modern industrial agriculture landscape. In previous centuries, farmland agroecosystems were diverse mixes of grazing land, crop land, orchards, wetlands and managed forests, which could support a wide array of biological diversity. Today, however, most industrial agriculture landscapes plant crops “fencerow to fencerow,” meaning the amount of harvestable land is maximized for the greatest profits, which has resulted in a reduction of the diversity of agricultural landscapes, in turn reducing agroecosystem biodiversity. 13