Robert Hijmans weighs in with his second posting from the domestication front lines. Thanks, Robert. Previous post here.
Change. Obama wants it, McCain wants it, I want it, and perhaps you want it too. Farmers just do it. At least that seems to hold for many of the farmers living in the major agrobiodiverse areas. While they maintain diversity, it changes all the time. Whether deliberate or not, as time goes by farmers will never quite have the same set of varieties or genes. That was one of the main story lines of today’s presentations at the Harlan II symposium in Davis, California.
Jan Salick sampled the cassava varieties of a community in the Peruvian Amazon. In a period of 10 years most varieties were replaced, probably to get rid of virus infestation and other forms of degeneration. But people very actively exchange and spread new varieties. And while not all farmers select from spontaneous seedlings, some do. This practice seems very important in this otherwise vegetatively propagated crop; an observation also made yesterday by Doyle McKey. But how common? We seem to know little about that. There are also cases of relatively little change over 40 years, as documented by Karl Zimmerer for potatoes near Cusco, Peru.
Change in diversity is hard to measure. Yes, even current patterns are hard to measure without going the whole nine yards of molecular biology. Toby Hodgkin showed how variety names can be poor markers for genotypes. But farm level variety data from “in situ conservation” projects in several continents revealed some general patterns (see this paper) about the number and relative distribution of varieties. Whether these patterns will hold to be general I do not know, but they do provide a benchmark. That is useful. In situ conservation should be less about good intentions, and more about data and consequences.
Hodgkin and collaborators also described the importance of seed exchange networks. Millet farmers (mostly women) in Mali go to the market to exchange seed they will take home to try. If the seed are any good some genes will likely end up in their populations.
In many of these agrobiodiverse, and often marginal — ecologically and/or economically — areas the Green Revolution has not made much of a difference. It seems to me that knowledge of these exchange processes that maintain crop diversity should not be only used to think about how to conserve it in situ. It could be more important to think about how to make use of these networks to insert new diversity. Not as the perfect high yielding variety, but as diverse sets of reasonably adapted genotypes with interesting traits that could be incorporated into the farmer’s populations. Building on existing processes that allow for local resilience and adaptation seems to be a good strategy in the light of the rapid climate change and other changes we are witnessing and expecting to see more of in the future.
We really do not seem to know that much about what is going on. The global village is big place. But at least some are trying. Gary Nabhan is one of them. In a copious lecture he discussed some of the material in his recent book describing his efforts to follow the footsteps of Vavilov to asses change in the areas where the great man collected.1
Nabhan found fewer apples near Alma Aty, the city of apples (and formerly of speed skating, I would add). Crops moving upslope in the Pamir mountains as its glaciers melt. In Ethiopia, wheat and barley are diminishing, giving way to a boom of the indigenous teff. The old crops of the southwestern USA are about to go extinct.
It is hard to generalize, but overall the news is not that good if you care about agrobiodiversity in the field. It does not seem to be going up in many places. Or is it?
Not too long ago, there were a million hectares of a single potato variety “mira” in southern China. Farmers had no idea that other varieties existed. I do not know what the situation is right now. But if is important to have agricultural biodiversity in the field, it will perhaps be more effective to increase it in crops and areas where diversity is low than trying to maintain it in areas where it is high.
Without understanding the context of the farming systems and the drivers and patterns of change, it is difficult to say something sensible about the fate of agrobiodiversity. I think the symposium organizers realized that. We had Bill Turner talk about the collapse of Mayan agriculture — which was likely related to overexploitation. What used to be the home of one of the worlds most advanced cultures is today a rather empty land with few people and not much natural biodiversity either. Karl Zimmerer discussed more current land use patterns and change near Cochabamba, Bolivia. Male outmigration, leading to remittances and investments in irrigation. Fewer potatoes, more peaches…
We are moving forward in our understanding of the use of biodiversity on farms. But the world is changing much faster still. This is affecting agrobiodiversity in unprecedented ways. We need more data, we need more synthesis. We need it soon.
- Rumor has it that a certain Jeremy Cherfas is setting up a blog devoted to this