Diversity is the spice of life, and biological diversity in many ways underpins so many aspects of food, from its nutritional value, its flavor and taste, and even how it is produced. I’m typically not one to argue for silver bullets, but food diversity is our best bet at long-lasting sustainability, and a food production that works with, rather than against nature. Let’s start with clarifying some terms however.
Many forms of diversity are involved in healthy and sustainable food. Dietary diversity, which may be the first thing that people think of when we speak of food diversity, is the diversity of foods that we eat.
By some estimates, there are 30,000-60,000 species of edible plants, in additional to countless species of edible fungi, algae, fish and shellfish, and animals. Eating a diversity of foods is generally considered the core of a healthy diets – particularly eating a diversity of plants and plant parts: fruits, stems, leaves, roots, seeds. Michael Pollan in his book Food Rules reminds us to “eat your colors”, this makes sense since the green, red, yellow, white, orange, and brown colors of food often represent distinct and complementary nutrients. The recent EAT-Lancet Commission’s Planetary Health Diet recommends that half of our diets be comprised of fruits, vegetables and seeds, with 30% of our caloric intake coming from whole grains – rice, maize, and wheat certainly, but why not teff, fonio, sorghum, millet, or other pseudo-grains like buckwheat, quinoa and amaranth? And a greater variety of plant-based proteins such a beans and pulses (0-700 grams per week).
Dietary diversity can have two important links to sustainable farming. First, eating a diversity of foods can support farming practices that grow crops in environments where they are best suited, and create markets for a diversity of foods, hopefully allowing farmers to select crops that are adapted to soils, climate, water availability. Our over-dependence on a handful of crops has driven a style of farming that has sought to adapt crops to different environments; or more recently new forms of hothouse or vertical agriculture that adapts the environment to a crops needs. Agroecology, in contrast, tries to find the best crops for a specific environmental condition. The second way that dietary diversity can impact the environment is by increasing our consumption of plant-based food, with more moderate consumption of meat. The EAT-Lancet Commission’s Planetary Health diet recommends 0-200 grams of beef, pork or lamb per week, 0-420 grams of poultry per week, and 0-700 grams of fish per week.
Livestock is an important part of circular agriculture; cattle and other grazers can be important means of conserving grassland plant, bird, and animal diversity in grassland biomes, thus the recommendation is to consume moderate amounts of animal meat, favoring farmers whom work hard to humanely produce quality food while protecting biodiversity and the environment. Overconsumption of meat is one of the biggest drivers of climate change and can be a major driver of biodiversity loss when forests are cleared for meat or forage production.
Often forgotten in food diversity, is the biodiversity that supports food production. There is a highly invisible workforce of bacteria, fungi, insects, birds and other critters that contribute to the production of high quality and nutritious foods. Increasingly we are becoming comfortable thinking about bees and the pollination services they provide, but entire soil ecosystems are frequently taken for granted yet critical to sustainable food production. Even less understood are the evolutionary forces behind healthy foods. What foods we eat have little impact on sustainable production – however how food is produced, and where it is produced make or break the sustainability questions. Let’s take these one by one.
Field scale practices are critical to sustainability. Health professionals and the public are increasingly understanding that the guy microbiome (the diversity of critters living in our guts) are essential to human health. A plant root, is simply a gut turned inside out. It is where nutrients are absorbed to allow for plant growth. Roots are surrounded by fungi, bacteria, and all sorts of other biodiversity which drive nutrient cycles, capture and store carbon, and filter water. Practices that limit soil disturbances such as no-till; or which limit the use of agricultural chemicals, particularly biocides (fungicides, herbicides, pesticides) but also fertilizers can help support healthy soil ecosystems (soil microbiome). Leaving plant material on soils, and cultivating a diversity of crops, either through polycultures or through rotations are key means of keeping biodiversity health, and functioning.
Biodiversity is essential around fields as well. Keeping wild vegetation around a field, or in a field as in agroforestry systems (trees mixed with crops) creates habitat for species that can contribute pollination or pest control services. The Planetary Health diets calls for increasing consumption of a diversity of fruits, nuts and vegetables because of their nutritious qualities. These are also the crops that are most critically dependent on pollinators, not just European honeybees, but on a diversity bees, flies, moths, butterflies, beetles and other critters. Wasps, ladybird beetles, and other biodiversity in contrast can play important roles preying on crop pests and keeping diseases in check. Cultivating a diversity of crops, reducing disturbance of soils and vegetation all serve to maintain habitat in and around fields and are important means of conserving the biodiversity that support healthy food production.
Let wrap up with a quick note on the most poorly understood interactions between food diversity and sustainability: evolution. Many of the flavors such as spicy chili peppers, aromatic cinnamon, or the bitter taste of arugula are the product of the evolutionary chemical warfare between plants and their predators. The flavors that we have come to enjoy where developed by these plants to protect their leaves, seeds and stems from insect, fungal, or other pests. Thus while pests can be pesky, they are in fact the source of the spice of life. We’re still not quite sure what happens to these flavors if plants are grown in environments where they are fully protected from pests, but one hypothesis is that they will eventually lose those flavors, and unique chemical properties such as antioxidants, which make them particularly nutritive and delicious.
We live in a uniquely biological planet. Diversity, in all of its forms is the hallmark of life. Protecting and working with diversity, rather than against, whether the diversity in our guts, on our plates, or in and around our fields is likely to be the best path to both health and sustainability.