An organic farmer I know feels that he is feeding a disproportionate number of his neighbourhood wildlife. It seems they prefer his organically grown crops to the sprayed and fertilized hybrid and GMO crops grown by his conventionally-farming neighbours.
The study described in this post talks about how birds prefer to eat the seeds of wild plants rather than farmers’ crops. One wonders whether the farmers in question are conventional or organic and if they are conventional (as most farmers are) that might explain why the birds would rather eat weeds.
“Call it the bird tax—or rather, the amount of food that farmers need to set aside in order to get birds to stick around and stop dying. Farmers don’t historically have an awesome relationship with birds [PDF], but in recent years, they’ve actually been paid to scatter grain around their land after the harvest, since a lack of seed resources in winter is thought to be one of the reasons for birds’ dramatic decline. Some of the seeds farmers spread around the edge of their fields are also attractive to pollinating insects, which is also thought to be good, since birds like to eat insects too.
Why put so much effort into attracting birds to farms? Well, the steady decline of most birds in the world and the increase of the human population are related—and, idealism aside, there’s only so much that wilderness conservation can do to alter that trajectory. And so a fascinating and pragmatic branch of science is developing. It asks the question: Is there a way to feed wildlife, while feeding ourselves?
One recent study took a close look at this question. A team of four scientists in the United Kingdom spent a year collecting dirt from all over an organic farm near Bristol, which grew mostly clover, oats, wheat, and barley. Their goal? To determine just how much food a farm that grows crops to feed humans also provides for wildlife. What they found: that weeds play a surprisingly important role in attracting and feeding birds—in fact, they might be key to farm biodiversity.
The soil sampling was a complicated operation. “You know you can get those leaf blowers?” says Darren Evans, the lead researcher on the project, during a recent phone interview. “We modified one so that it sucked rather than blew.” The group sampled 250 spots around the farm and, after drying and sifting the dirt collected, found themselves with 171,000 seeds. “We counted and identified every single one,” Evans adds, sounding a bit weary. “It took a long time.”
The team managed to identify 156,000 seeds from about 125 different plants. They tallied the energy content of each seed species and estimated that the 300-acre farm contained 33 metric tons of biomass and 560 gigajoules of energy that could be ingested by local wildlife—most of it in the form of seeds and berries.
However, most of the seeds also happened to be from plants that the farmer in question never had any intention of growing. The two most energy-rich sites on the farm were areas where crops hadn’t been planted, either. What this meant was that most of the high-quality bird food on the ground was coming from weeds.
This is not a huge surprise. Most plants in the world exist because someone likes to eat them. Our favorite crops have spread all over the face of the earth because we like them enough to plant them, water them, and interfere in their sex lives. And some believe weeds spread far and wide because they provide food to animals and insects, who carry their seeds with them on to their next destination….”