Agroecology – science for a sustainable agriculture


I’m teaching Sustainable Agriculture again this fall at the University of Massachusetts and one of the questions that often arises is “what sort of research should the university be doing to move us toward a more sustainable agriculture.”  I’ve been thinking about this for a long time – the answer is agricultural systems ecology (or agroecology for short).

Agroecology is the framework which will allow us to scientifically address multiple interrelated objectives of economic viability, social equity, and environmental integrity. An agroecosystem may be a field, a farm, or a larger region such as a river valley.  Implicit in agroecological research and education is the idea that knowledge of ecosystem relationships will allow farmers to manage inputs and processes in agricultural production systems and thereby optimize for productivity, sustainability, stability and social equity.

A systematic research method for agroecosystem analysis was described by Gordon Conway, of the Centre for Environmental Technology at the Imperial College of Science and Technology in London (Conway, G. 1985. Agroecosystem Analysis. Agr. Admin. Vol. 20:31-55).  Agroecosystem analysis is based on ecological principles that govern relationships among biotic (living) communities and the abiotic environment.  Biotic relationships may be described by principles of predator/prey interactions, competition for food sources and habitats, cooperation and commensalism etc.  Abiotic relationships are described by nutrient cycling, carbon cycles, energy cycles, etc. over space and time.

Conway suggests that four system properties may be used to understand the dynamics of an agro-ecosystem.  They are;

  • productivity,
  • stability,
  • sustainability, and
  • equitability.

Productivity is the quantity of product or output from an agroecosystem per unit of some specified input. For an agroecologist, output may include a marketable product such as bushels of corn, as well as negative products of a system like water runoff, pesticides leaking from the system, or soil lost. Of course, tons per hectare is a standard measure of productivity. But productivity can also be expressed in other units of output per unit of input. Inputs may be measured in tons of fertilizer, monetary value of pesticide, or kilocalories needed to deliver irrigation water.

Stability is consistency of production in spite of short term upsetting influences such as uneven rainfall, pest explosions, price variability, etc. Annual variations in productivity indicate a lack of stability.

Sustainability is the ability to maintain a desired level of production over time, in spite of long term destabilizing influences. Examples of these are; increasing soil salinity, off-site effects of soil erosion, declining market prices, or accumulation of biotoxins in the environment. Systems which rely on heavy inputs of non-renewable and rapidly diminishing resources are not considered to be sustainable. Sustainability is a measure of persistence or long-term resilience of a production system.

Equitability can be used as an indicator of agroecosystem performance which incorporates the social dimension. Social equity is a measure of the degree in which resources and products of a production system are equally distributed throughout the human population. This implies that equality of product availability (output) and equality of resource availability (inputs) are the preferred norm.

A research and/or educational institution that employs agroecosystem analysis will probably conduct more studies on complex relationships among the various components of a agroecosystem that go beyond simple cause and effect.  There will be more research on inputs and outputs that are measured in currencies other than monetary units, such as carbon, nitrogen, and calories.  This will provide the basis for better nutrient management recommendations. There will be more studies on relationships among pest populations, predator populations, host populations (both agricultural crop and non-crop species), and environmental influences on these. This will provide the basis for better pest management recommendations. There will be more studies on interspecific relationships among crop plants and the effect of these on pest populations. This will provide the basis for innovative multiple cropping systems.

Ecological principles will provide an appropriate framework in which to better understand and manage the impact of agricultural systems on the food supply, the environment and people. I believe that ecological approaches to agriculture can be the common ground upon which we address the needs of society, while employing the tools of scholarly research and teaching, for which public institutions are best equipped.


This paper was presented by John Gerber,  as part of a U.S.A.I.D. sponsored workshop on sustainable agriculture in Lusaka, Zambia, September 18-21, 1990.


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Please join the “buy local food” movement – and invite your neighbors!


It’s harvest season in Western Massachusetts and everywhere I look I see wonderful local food products for sale.  We have vibrant farmers markets, colorful farm stands and productive farms in my region of the world.   And of course, I have my own very large garden that is producing tomatoes, peppers, cucumbers, eggplant, blackberries, green beans, Asian pears, eggs, honey and more this time of the year.  So I am surely not objective when it comes to local food.  I think about it, talk about it, and participate in growing and buying local food whenever I can.

I’ve written in the past about the need to relocalize our food system to support democracy, to build a vibrant local economy, and to move us toward a more sustainable agriculture.  One might think I’d have nothing more to say about local food, but when I was asked recently to speak at celebration of local food in the nearby town of Granby, Massachusetts, I was moved to write yet another blog!   Here is the outline of what I said……

While it is easy to celebrate local food this time of the year, I am concerned that an increasing number of farmers are competing for customers in a market that is not expanding as fast as production.  We need more people to buy local – and we need your help to make this happen!  Most people buy their food at “big-box” stores (Walmart is the largest food retailer in the world).   We need your help to build a local food economy that will offer some balance to the industrial food system and give us a bit of insurance against collapse, soooooooooo….

…I’m asking you to join the “buy local food” movement and be sure to invite your neighbors! 

If you are going to help, you might first think about what you’d say to your neighbors, who don’t participate in the local food movement.  Here are a few of my own thoughts…..

“I care about good food….  my local community…. and my connection with the sacred.”

1.  I care about good food and we know that local food is “fresher by miles.”   The average food item on your plate has traveled from 1300 to 1500 miles to get there.  And in spite of advances in packaging, refrigeration and handling (which are very energy expensive), sweet corn loses its sweetness within hours of picking…. and there is really nothing like an egg collected “direct from the hen”  and eaten on the same day.  Really… try it!

While some food items ship and store well, such as potatoes and squash…. even with these, you should try a local potato like the yellow, orange, or purple skinned fingerling potato (halved and roasted).  And while one might think that squash is squash is squash….. it is difficult to get the thin-skinned Delicata squash (you can eat the skin) except from a local farm, as it bruises easily when shipped.  I grow my own.

I also care about safe food, and quite frankly I don’t trust the industrial food system to keep my food free of pesticides and anti-biotic resistant bacteria and other human disease organisms (like bird- an swine-flu.  You may not want to know….. but there is a food recall by the U.S. Food and Drug Administration every few days, and Congress has threatened to reduce the inspections budget.  Last summer’s salmonella tainted eggs in the American Midwest was unfortunately not a surprise.  I much prefer to look into the eye of the farmer from whom I buy my food.


2. I care about my local community, and I much prefer that any money I spend on food stays close to home.  When I spend my money at a Super Walmart grocery store (I don’t), that money leaves the community.  The purpose of a corporation is to  generate profits for investors….. that’s all!  Recent reports of how CEO salaries have skyrocketed makes me sick.  When I buy bread from Ben and Adrie Lester at Wheatberry Bakery, I know my money is going to people I know and trust.

A study comparing a locally owned bookstore and a national retailer found that $100 spent at the local store resulted in $45 circulating in the community through services such as banks, bookkeepers, accountants and advertising etc.  This compares with only $15 from a national chain.  When you are talking about food rather than books, the difference is even more dramatic.  The Local Multiplier Effect is an important contributor to our local and regional economy, creating jobs and building relationships close to home.


3. I care about my connection with the sacred, so I buy local.  Okay, so this one isn’t quite as obvious as the other two reasons.  I wrote in an earlier blog…. “Putting food in our bodies is the most intimate act we do on a regular basis.  Eating food can either be a sterile, hurried act, offering little cause for joy – or a creative, spiritual act of connecting with other people, the earth – and thus with all of Creation.”

Rediscovering the sacred through growing or purchasing and preparing good food can be an act of healing.  Shopping in a supermarket with its artificial lighting and hurried atmosphere is not a sacred act.  We seek and receive bargains, hurry home to microwave a pre-prepared package  (or perhaps stop for ‘fast-food’ on the way) and thoughtlessly shovel too much food into our hungry bellies (maybe while watching television).

Perhaps we can experience a connection with the divine……..

  •             by collecting an egg from under a hen you have raised yourself…
  •             by pouring maple syrup on pancakes from a tree tapped by a neighbor…
  •             by knowing the baker of the bread (or better yet, baking it yourself)…
  •             by  shaking the hand of the farmer who dug the carrots you bought…
  •             by saying thank you for the gifts of creation; the fruit, the vegetables, the meat, the eggs, the bread and the wine…..

I believe there is value in rediscovering ways to connect with the sacred by growing our own food,  buying real food from people we know and trust, and sharing food with family and friends in a communion of the spirit…

So, yes…. I support the local food system whenever I can.  Are you willing to join me… and invite few of your neighbors?


I’d appreciate it if you would share this post with your friends. And for more ideas, videos and challenges along these lines, please join my Facebook Group; Just Food Now. And go here for more of my posts.