Today marks Blog Action Day 2011 — an annual event that unites the world’s bloggers around the same issue. This year’s topic? FOOD. Cool Green Science asked Joe Fargione, lead scientist with The Nature Conservancy’s North America Region, to share his thoughts on a food topic we’re often asked about: is organic food better for the environment? Here Joe explains the trade-offs between buying organic foods and using less land through conventional farming practices.
Growing crops has several impacts on the environment. Crop production takes land, water and other inputs which can include synthetic fertilizers, herbicides and pesticides (all of which can be either synthetic or natural). Let’s discuss each in turn.
Organic crops do generally have lower yields and therefore require more land. This has been shown in randomized experimental designs and on real farms. In 2008 the United States Department of Agriculture conducted its first ever survey of organic producers, collecting data on acreage and production from over 20,000 organic farms.
The results of this survey were published in 2010, allowing a comprehensive, crop by crop, comparison of yields between conventional and organic production for the first time. The data are conclusive: comparing 62 crops – from almonds to watermelons – conventional yields are 10%-360% higher than organic yields.
There are a few (four) exceptions: organic tomatoes, sweet potatoes, canola and hay are higher yielding than their conventional counterparts.
This means that if all of our crops were organic, they would take substantially more land. For example, if all of the corn grain, winter wheat and soybeans in the United States were grown organically, it would require about 93 million more acres of farmland, a 30% increase in total crop acres.
Of course, if you want to reduce the amount of land required to produce your food, you can always eat less meat or buy grass-fed meat. Grain-fed meat production requires a lot of land – over a third of all cropland in the United States is used to produce livestock feed and forage – so eating less meat means using less land. And grass-fed beef, bison or other free-ranging livestock require grasslands for grazing, and these grasslands often provide habitat for lots of species – its own form of habitat preservation.
For water use, I’m not aware of studies comparing conventional and organic farming. But since organic certification doesn’t require lower water use, I see no reason to expect any difference between water usage in organic versus conventional crops. Similarly, both conventional and organic methods can cause soil erosion that contributes to sediment pollution in rivers. One of the best solutions to sediment pollution is no-till farming. But organic farmers have traditionally used tillage as a form of weed control, making it difficult for them to switch to no-till farming.
Organic crops use manure fertilizes, which unlike synthetic fertilizers, contain organic matter that helps build soils. But both organic and synthetic fertilizers can contribute to run-off of nitrogen and phosphorus into streams and rivers. Synthetic fertilizers tend to cause more nitrogen pollution to surface and groundwater, whereas manure application tends to cause more phosphorus pollution to surface waters.
It should be noted that both types of fertilizers can be applied responsibly by using the correct amount of fertilizer at the correct time and using tillage practices and buffer strips that slow runoff and reduce the loss of nutrients from farm fields. One challenge particular to manure fertilizers is that the ratio of phosphorus:nitrogen is high compared to the demands of the crop, so that if you add enough nitrogen you are likely to add too much phosphorus.
When it comes to toxic pesticides, organic farming is the clear winner. In a comprehensive nationwide USGS study of 186 streams and over 5,000 shallow wells, pesticides (or their byproducts) were detected in every stream and more than half of shallow wells in agricultural and urban areas. Conventional agriculture used 877 million pounds of pesticides in 2007, the last year for which data are available.
Pesticides kill significant numbers of birds and other non-target species each year. In addition, these pesticides are generally not good for anything that lives in or drinks water.
For example, the European Union ranks pesticides according to their impacts to aquatic organisms; essentially all of our conventional pesticides are considered either harmful, toxic, or very toxic to aquatic organisms. Encouragingly, conventional agriculture has doubled the proportion of pesticides that are only “harmful or toxic” from 20 to 40% between 1999 and 2007 (reducing the proportion of “very toxic” pesticides from 80 to 60%). And the total amount of pesticide that is used every year decreased by 8% between 1999 and 2007, even though food production has increased. But on balance, conventional food can’t compete with organic food when it comes to environmental impacts of pesticide use.
Life is full of tradeoffs, and this is no exception: Organic foods require more land, but don’t use synthetic pesticides.