Of all the myriad species of plants or animals whose products are useful to people, agriculture directly uses only a few hundred. Some twelve plant species provide approximately 75% of our total food supply, and only fifteen mammal and bird species make up more than 90% of global domestic livestock production.
What is not generally appreciated is that these relatively few species depend for their productivity on hundreds of thousands of other species. Among the latter are insects and birds that pollinate crop flowers and feed on crop pests. Even more numerous and diverse are the microbial species that live on, and in, plants and animals and that are especially abundant in soils. These serve, among other functions: to protect against pests, decompose wastes and recycle nutrients so that life can regenerate, convert atmospheric nitrogen to soil nitrogen compounds vital for plant growth, and live symbiotically in association with crop roots to facilitate the uptake of water and nutrients.
Many organisms, including birds, bats, shrews, moles, frogs, toads, salamanders, dragonflies, wasps, ladybugs, praying mantises, soil roundworms called nematodes, and spiders, serve as natural pest control agents in agricultural systems.
Others, such as humming birds, butterflies, moths, honeybees, bumblebees, wasps, beetles, and bats pollinate flowers, including those of many important fruit and vegetable crops, such as tomatoes, sunflowers, olives, grapes, almonds, apples, and many others. More than 80% of the 264 crops grown in the European Union depend on insect pollinators.
Genetic diversity in crops reduces the odds of crop failure secondary to changing weather, protects against the spread of plant diseases and attack by plant pests, and can lead to greater yields. As agriculture continues to rely on fewer and fewer species and varieties of crops and livestock, and as wild relatives are increasingly threatened, the need to preserve the genetic diversity of crop species and domestic animals for future generations grows steadily, increasing the importance of seed banks and other measures.
In spite of some significant questions about genetically-modified (GM) crops that remain incompletely answered, including about the risk of such crops’ invading natural habitats and hybridizing with wild species, and about the toxic impacts from the herbicides used in some GM farming on non-target species and on biodiversity in general, the planting of GM crops worldwide continues to expand each year by double digit percentages.
Organic farming has been shown, in general, to be more energy efficient and drought resistant, and significantly better at preserving agro-ecosystem biodiversity than conventional farming. Many studies have also shown comparable yields for organic and conventional methods for some crops under normal climate conditions, and there is much evidence that organic farming can be scaled up, as was shown in Cuba, to feed very large populations. In addition, those eating organically grown food have lower exposures than those eating food grown conventionally to a wide range of pesticides and other chemicals, about which there is little to no data on long-term human toxicity. And yet, organic farming is rarely included as an option in discussions about future world food security.
In the oceans, as on land, only a few species comprise a significant proportion of the total seafood harvest consumed as food, with the ten most harvested species accounting for approximately one third of the total. Over-fishing has reached crisis proportions in the world’s oceans, with the FAO estimating that about 70% of commercial marine fisheries are being fished unsustainably. The by-catch of other organisms from these operations, such as other fish, dolphins, and sea turtles; the damage to fish-breeding and nursery habitats, such as coral reefs and mangroves; and bottom trawling are especially destructive to the marine food chain. Industrial fishing practices have reduced the total mass of large predatory fish in the oceans to only 10% of what it was 40-50 years ago.
Freshwater fisheries produce about one-quarter of the world’s food fish, but these are increasingly threatened by the degradation of rivers, lakes, and streams; by their impoundment by dams and diversion of their waters for agriculture; and by growing levels of pollution.
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