Grassy desert: Changing nature of ag production

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Farm Forum

The jury is still out as to whether the extreme drought conditions that continue to grip more than half of the country are the result of global climate change, but the majority of scientists do believe that a major shift in weather around the world is occurring.

Among the believed effects of this phenomenon will be increased stress on agricultural production. According to his research, Washington State University entomologist David Crowder finds that climate change is expected to contribute to both habitat and species loss globally. But, surprisingly, the weather change should result in an increase in agricultural productivity in the Yankton area and much of the upper half of the Northern Hemisphere. The same can’t be said for the rest of the world. To compound the problem, due both to changing ecosystems and growing urbanization, arable land worldwide is decreasing.

At the same time, the demand on agricultural production will rise sharply as population growth continues, Crowder says. While the population in developed nations, like the United States and much of Eastern Europe, will remain steady, others will be gaining.

“A lot of human population growth that is accelerating climate change is in less developed countries in Asia and Africa,” said Crowder, whose research centers on insect biodiversity of agricultural systems. This will not only stress agriculture by putting on more demand for food, but also by adding to greenhouse gas production and the climate change effect.

“Obviously, this presents a big problem for the human population as a whole,” Crowder said.

So, human survival isn’t just a matter of increasing yields, as many of the technologies to do so – synthesized fertilizer application, for example – also contribute to climate change, he adds.

Specifically, Crowder’s research focuses on agricultural insect pests, and like other mostly conventional farming practices, chemical insecticides add to the climate change problem – both through fuel usage of the sprayer as well as changing the cropping ecosystem.

“Climate change is reducing biodiversity, and some farming practices can promote biodiversity,” he said.

Ecosystems, and the species that live within them, have an intricate interaction with the climate. Easily forgotten is that the climate also reacts to long-term changes in the ecosystem. For example, 200 years ago, the Yankton area was a prairie as far as the eye could see and the climate was drier. Over the last century, as the landscape turned into mostly row-crop cultivation, so has the climate changed.

Al Dutcher, University of Nebraska state climatologist, said that the Great Plains was once referred to as a grassy desert and that, during the past 30 years, the Upper Midwest has been in an overly wet period.

As cultivation took hold in the heartland, the overall ecosystem of the Great Plains changed and so did the species it contains as well as that species’ behavior, Crowder says. He blames agricultural production on increasing insect pest outbreaks in the United States.

“If you’re a bug, you might see a field of crops as an all-you-can-eat buffet,” Crowder said.

His hope is to find farming practices that alter the behavior of insect pests accustomed to cultivation, that lead to increased insecticide use. Crowder considers both conventional and organic cropping systems in his research, seeking out an ecological-economic balance between the two.

Conventional farming practices consist of calendar-based sprays of broad-spectrum insecticides and soil fumigation that kills all insect species it comes in contact with. Organic farming practices consist of natural pesticides and bio-fumigation that targets specific insect pests but tries to leave insect biodiversity alone. In conventional farming systems, there is a 15 percent increase in yield over organic practices but there is a definitely different environmental impact between the two.

Interestingly, in his research, Crowder finds that conventional pest control doesn’t eliminate all insect pests. Rather, it disrupts the natural biodiversity so that while there are fewer insect pests, pathogen incidence rises instead. However, organic methods are not any more effective at protecting biodiversity balance: While organic farming’s aim is to preserve predator insects, the result is also more insect pest numbers. However, to organic’s credit, there is no negative effect on other forms of biodiversity balance that help to control pathogens as well as enhance natural pollination, soil nutrient cycling, and other natural processes that are harder to achieve in conventional systems.

“Organic increases the number of organisms but does not increase biodiversity more than conventional, but at the same time, there is a more equal proportion of species,” Crowder said. “Conventional has the same biodiversity as organic, but the species have fewer numbers and some species are represented much more or much less than others.”

Whether conventional or organic, whether using broad-spectrum insecticides or not, what makes insect pest control effective is not how many insects are killed or even certain species of pest insects targeted, but rather what balance of insect predators are achieved for the cropping system, Crowder says.

“Not all biodiversity is a good thing,” he added. “You really have to understand the interaction of all the species.”

Imagining a pie chart, Crowder says, the goal is for all predator insects to be present in equal abundance: Most cropping systems, whether conventional or organic, have disproportionately higher percentages of one predator insect than others – more than half of the pie chart; the goal is for all insect predators to have an equal piece of the pie.

“It is a more balanced community when everybody is doing their job,” Crowder said. “If you have 100 people in a town and 99 are barbers, there are a lot of jobs not getting done.”

Most predator insects don’t have specific insect pest species that they prey on, he says, but they all have a part in an ecosystem in how the species interact. So, even if one predator insect species is present in large numbers, they interact with the ecosystem differently than if all predator insect species were present in equal numbers.

“In more balanced systems, we see greater numbers of natural enemies,” Crowder said.

Furthermore, his research shows that equal proportions of all predator insect species not only increases insect pest mortality but also increases plant biomass, meaning that plants are larger and more productive.

Certain crops are more likely to see an advantage from this biodiversity “evenness,” as Crowder defines it: Soybean yield would benefit more so than corn, he said. In addition, farms with more crop diversity will tend to achieve biodiversity evenness easier.

“It may seem these little shifts of balance aren’t important,” Crowder concluded, “but they can really move in your favor as far as improvement to your yield.”