Sometimes scientists seem utterly clueless.

"In essence, the data in the article strongly supports a new explanation for why the world contains so many species," said Tilman. "It shows that plant diversity is directly related to the number of limiting factors (such as soil moisture, nitrogen, phosphorous, potassium and water)."

It also helps explain why grasslands, lakes and rivers that are polluted with nitrogen and phosphorous (usually from agriculture) have fewer species. The reduction of species where the Mississippi River empties into the Gulf of Mexico is one of the best known examples of this phenomenon.

The findings are based on experiments carried out at the University of California?s Sedgwick Reserve in the Santa Ynez Valley, where the researchers applied combinations of nutrients and water to plots of grassland. Plots that received all of the resources had the fewest species and highest productivity. They combined this with analysis of the 150 year old Rothamsted Park Grass Experiment. Both supported their hypothesis.

"Our results show that the loss of plant species from a habitat due to nutrient pollution can persist for more than 100 years," Harpole said. "Thus human actions that simplify habitats can lead to long-term loss of biodiversity."

This has been known for centuries, probably longer. You get what you manage for, whether you understand what that will be or not. Any change to a sward will favor some species over others. Increasing fertility will favor the species most able to exploit high fertility, making them more competitive. It's a jungle out there.

But, the effects aren't one off. The species that don't prosper under a given management regime decline, but others that couldn't get a toe hold before will begin to take their places. Over time diversity will likely increase again, but with different species than in the original sward.

If you are not aware of these dynamics, you will have unexpected results. And if you are a scientist it seems that you will be completely flumoxed. A wise grazier won't be fooled, won't expect the film to be like the novel, and will adapt management as the specific changes emerge. It's a process, not a project, and never ends.

Fertility management is used explicitly by graziers to manage sward composition. You can get rid of some "weeds" by simply doing good fertility management. Conversely, it does you no good to plant some cultivars unless you also intend to maintain high fertility, since their desirable characteristics and persistence depend on it.

Other soil characteristics such as PH and moisture are managed in the same way. You balance sward conditions to favor desirable species, but not so much that you also encourage others that are less so. You may lose some productivity, but also avoid infestations that would in the end reduce productivity even more.

Is anyone educating these people?