I spent the last two days at the Young Farmers Conference in Tarrytown, NY. I gave an introductory talk on permaculture with Dyami Nason-Regan of Appleseed Permaculture, and a more in-depth talk on agroforestry. In addition to the standard agroforestry material, I talked a lot about the ecological character and land use history of the Northeast, and about ecosystem management and keystone species.
A lot of people attending the agroforestry workshop were farmers with small woodlots. And one of the things about small woodlots is, they often don’t have a lot of diversity, and in many cases lack connectivity with larger ecosystems. So landowners have a lot of “what can I do here?” questions. In particular, there were a number of questions about pig silvopasture, AKA “pigs in woods.” The Stone Barns Center where the conference was held is experimenting with this type of silvopasture and there was a lot of buzz about it at the conference.
Anyone who’s curious about this system should read The Omnivore’s Dilemma for inspiration, in which Michael Pollan gives a long profile of Joel Saletin’s Polyface Farm which uses pig silvopasture. Basically, pigs evolved as omnivorous forest and woodland animals in Eurasia. They eat lots of hard mast (i.e. nuts and acorns) and make more delicious pork when fed from such rather than from grains. And, it’s a multiple-functions use of maybe otherwise underused woodland. There’s a lot to like about this system both economically and ecologically.
They should also read William Cronon’s classic Changes in the Land as a cautionary tale. Pigs are a little bit like bears, creating a lot of small-scale landscape disturbance. This can create new diversity by opening up new niches for plants. But, pigs dig and root much more than bears, and they travel in small herds, concentrating their disturbance. So this means pigs can be very hard on the landscape where there’s thin or erosive soils, or where they’re stocked too densely.
And that’s exactly what happened across New England in the early colonial years. Pigs pastured in small fields and meadows created more soil disturbance and erosion than the local deer ever had, sedimenting previously clear-flowing streams. And, pigs released to roam wild in the forest (as many were) vacuumed up hard mast that other species* depended on. In the fall, when European colonists would hunt down the pigs for slaughter, some would always escape being hunted and form feral populations, which could persist and reproduce for generations. So a new, high-soil-disturbance omnivore introduced into Northeastern landscapes contributed to (in concert with widespread deforestation and other land use changes) the eventual extinction of the passenger pigeon and near-extinction of many anadramous fish. Look before you leap.**
Check out YFC for next December, and check out my agroforestry presentation below.
*Like deer, bears, turkeys, passenger pigeons, squirrels, and of course humans.
**There’s more to this story, of course – a lot more. Pigs had at most a tertiary role in these extirpation/extinction events. And in some places wild boars have become an integrated and mostly non-destructive part of the recombined post-colonial ecosystem. But it’s a reminder to make mistakes on paper, and to design new systems thoughtfully and conservatively when there’s the potential for downstream impacts. Also, island biogeography.