"Sylvopastures'" Bringing Trees Back to Grazing Lands

Sep 2, 2016

Did you find yourself searching for shade during those hot, sticky weeks we’ve had this month?  Well, you’re not the only one. Grazing animals seem to like it too. But most farm pastures have few if any trees, because farmers believe they just hamper productivity.  That means animals are often subjected to the hot sun for hours on end.  Robbie Harris has this report on Researchers at Virginia Tech who say there are actually benefits to animals grazing in pastures with trees. 

Sheep like shade; sylvopasture test site at Virginia Tech
Credit Gabe Pent

“Nobody puts trees in their pastures.  That’s what I thought when I first started. The producers have been working for 30 generations to clear those trees.

John Fike, Associate Professor of Crop and Soil Environmental Sciences at Virginia Tech and his grad student Gabe Pent have been testing their hypothesis for the last 3 summers.

Pent says, "We’ve got a controlled system, it’s our open pasture without any trees at all, just kind of the conventional system and then we’ve got these ‘Sylvopastures,’ which are these integrated systems where we have trees growing with the forages.”

Silva, the Latin for forest sounds like the opposite of the word pasture, but together they recall practices farmers used for centuries before chemical fertilizer and easy tree removal created the wide-open spaces for grazing

“So we’ve got two different types of Sylvopastures, the Black Walnut and the Honey Locust.”

Sheep wearing microphones to track the sounds of their chewing; high pitched sounds mean they're grazing
Credit Gabe Pent

If their shade were a fence, it couldn’t do a better job of holding these lambs in place.  They lie on the ground in tree canopy shaped clusters.

“If they have shade they stay in it they move with it.  So they move with it very closely. You see those animals on the edge, the sun is moving and they're starting to come into the sun in about 5 minutes they’re going to get up and they’re going to move deeper into the shade.”

Trail cameras to follow the sheeps’ movement documenting their shade seeking behavior and to see how it correlates with grazing, they’ve given each sheep a microphone.

“So that’s recording them and the idea is that when grass is ripped, during a ‘prehension’ in an intake event a quick high frequency sound is produced.”

And sure enough sheep graze longer in the shaded pastures.  Kind of like the way we might sit longer at a table not right in the sun on a hot day.  This study showed that the shaded sheep gained about a third more weight than the control group.

“So you get the same animal product and you get these trees. So out of these Black Walnut trees we’re getting timber in the long term but we’re also getting nut production and those can be used for different purposes, feeding to animals or selling (the nuts.)" 

So if creating more sylvo pastures could add up to bigger profits for farmers. Professor Fike suggests there are other benefits to the whole concept of grazing animals among the trees that may not be as simple to put a dollar value on.

John Fike: “So sometimes we don’t have good ways to valorize the things that we see. How do I put a value on my being able to work in the shade?  How do I put the value on listening to these birds while I’m out here working? I can’t necessarily get paid for reduced rates of speed of rain drops hitting the ground and what that might mean in terms of reduced soil erosion, so there are a number of benefits that society or I, as an individual might reap that I can’t necessarily put a value on.”

Benefits that have been lost, say Fike and Pent, as modern farming methods replaced traditional practices.

Gabe Pent: “This might have been a more natural system in the southeast when we had fires and large ungulates, bison even in the piedmont prarie, who would come through and tear up trees but also leave a few trees here and there so this savannah- like system is actually probably more natural from an ecosystem perspective.  So we’re starting to look at some of the pollen records and some old text from the first explorers that this is actually how nature prefers to be so we’re kind of looking back at nature and seeing how she prefers to do it and trying to see how science can interpret that.”