This Nature Longread essay first appeared in SNAP Magazine, which features great writing on the intersection of nature and human well-being as part of the website of the Science for Nature and People (SNAP) collaboration. Read more SNAP Magazine articles and learn more about the SNAP collaboration.
The local food movement has captured the imagination of many foodies, chefs and gardeners. But is “going locavore” also good conservation — or just an exercise in feeling good?
The term “local” food has various and sometimes conflicting definitions. It often means food grown “near” the consumer (e.g. within 50 miles, the county, or the same state). It can also mean food sold in an alternative food market. And it could refer to food that has some characteristic reminding people of what they think of as home.
Regardless of the range of its meanings, the concept has undeniable power. The growth in the local food movement in the developed world has resulted in dramatic increases in numbers and sales from farmers markets. It has also spurred new (or re-emerging) marketing strategies, such as community-supported agriculture (Brown & Miller 2008).
There are myriad reasons that more and more people — myself included — are becoming locavores. Not only do we think that local food has better quality, we believe it can positively affect our health outcomes, boost our local economies, build sustainable communities and contribute to a better environment.
One of the main reasons consumers choose local foods is to reduce the food miles of their purchases — that is, the distance that their food travels from farm to plate — in an effort to reduce the greenhouse gas (GHG) emissions created by its production. If we consume more local food, we assume, we reduce our GHG emissions, slow the impending impacts of climate change, and thus contribute to environmental protection and conservation. Right?
Turns out, the calculation isn’t that simple. Food production relates to GHG emissions in many ways, and food miles are just one aspect of a life-cycle analysis for an agricultural system generally accounting for <15% of energy use to produce food products (Brodt et al. 2013, Plawecki et al. 2013).
We also need to consider high farm-to-farm variation in carbon stocks and carbon sequestration, production methods, food processing and retail processes (Edwards-Jones et al. 2008). Agriculture is a large consumer of fossil fuels for input production and application and mechanical harvesting.
The complex nature of life-cycle analysis is evident in these two examples:
- Sometimes local production does come out ahead in “cradle-to-grave” life-cycle analyses. In one comparison, Plawecki et al. (2013) compared the energy used in production of organic, hoop-house lettuce produced and taken to retail in Michigan with conventionally grown lettuce transported in refrigerated trucks from California. After considering energy use associated with diesel fuel burning, production of fertilizer and compost, farm production activities, transport, and manufacturing of inputs such as hoop-house and irrigation materials, they found that total emissions to produce 1 kg of lettuce were 4.3 times higher for California than for Michigan.
- But a similar life-cycle analysis that compared energy use for tomato production in Sweden and Spain for consumption in Sweden found that GHG emissions were highest for tomatoes produced locally (Carlsson-Kanyama 1998). That’s because only about one-fifth of the energy was required to produce tomatoes in Spain; Swedish production required high use of coal burning to heat the greenhouses needed for local production. So transport isn’t the only factor determining how efficient local food really is; we must consider whether the methods used to produce it were organic, conventional, field or greenhouse.
Thus locavorism doesn’t ensure general ecological sustainability in our agricultural systems. Where our food is grown makes no guarantee about the production methods used to grow that food and those methods’ subsequent impacts on the environment and biodiversity (McWilliams 2010).
While for many of us the term “local” conjures up images of environmentally friendly, small, locally owned farms, such farms are not implicit in the standard definition. And if local farms use industrial agricultural methods that include widespread use of agrochemicals and tillage, these practices will have tremendous negative impacts on biodiversity (Kimbrell et al. 2002). Using toxic agrochemicals may also have strong negative impacts on farm-worker communities, regardless of where the food is grown.
Take, for example, strawberries produced in Watsonville — a mere 20 miles from my home. Production of these local (to me) strawberries means heavy use of two soil disinfectants — methyl bromide, a destroyer of stratospheric ozone, and methyl iodide, a potent neurotoxin. In order to grow this local crop, biodiversity is harmed, soil microbes are destroyed, and pesticide drift looms over neighboring towns and schools (Reeves et al. 2002).
These strawberries may be local, but are they produced sustainably? Will consuming them improve my health compared with eating non-local strawberries? Will the production methods ensure biodiversity protection, provisioning of ecosystem services, and farmworker health? Seems not. Something more than “local” is needed in order to make combinations of agriculture and conservation work.
If we can encourage local food organizations that are doing excellent work in promoting the local food movement, health, and community food participation (e.g., Food Corps, the White House Garden, and the Slow Food movement) to also move towards supporting exclusively agroecological, sustainable and organic techniques, then local food may indeed protect biodiversity.
Agroecological production methods — such as intercropping, including crop diversity, conservation tillage, biological pest control, and planting buffer strips or hedgerows — ensure higher biodiversity protection (Altieri 1998, Harvey et al. 2008) and can lower carbon emissions (Lin et al. 2012). Moving towards a local food movement that is also agroecological will better promote conservation outcomes.
So what data do we need?
On the one hand, we need more data that can provide information about the economic, health and environmental impacts of local and non-local food. Such data is mostly lacking (Edwards-Jones et al. 2008). Pursuing an evidence-heavy approach to compare local vs. non-local will allow us to really determine whether local food purchases contribute more or less to GHG emissions — not to mention whether local food has higher nutrient content or contributes to improving health outcomes for urban populations. An accumulation of data from case studies from individual locations will allow us to build up to more global comparisons of when and where it is more ecologically and economically sustainable to eat locally.
Another approach is to look at the food that is produced locally (e.g. with local small-scale producers, at urban and community gardens) and collect data on how we can manage these sites so that they are more sustainable.
How, for example, can urban or local agroecosystems be managed so that they yield more food and food of higher nutrient quality? Suffer from less soil erosion? Contribute to the biodiversity conservation of organisms that provide important ecosystem services such as pollination and pest control (Philpott et al. 2014), or so they contribute less to carbon emissions (Kulak et al. 2013)? We can continue to search and investigate trade-offs between sustainable livelihoods for farmers and conservation outcomes in local settings, wherever that may be.
As a final note, how you define “local” food may be dramatically different depending on your cultural, ethnic or racial background. Local food in many tropical regions doesn’t mean becoming a locavore or a local food purchaser; it is already a way of life. We cannot underestimate the role of local subsistence agriculture in biodiversity conservation. And we need to recognize the important conservation role played by smallholder farmers in those developing countries that also harbor the most of the world’s biodiversity (Harvey et al. 2008).
We shouldn’t ask whether local is better than non-local, or whether local is better than organic. Instead, we should ask how to make all agricultural systems more sustainable — in order to promote food sovereignty, to empower local societies, and to sustain ecological communities in order to promote long-term conservation of habitats and of biodiversity.