The grasslands of the Rocky Mountain West serve as enormous catchment areas for some of America’s most important rivers. Though they are losing tons of soil to erosion and shedding water to the extent that flooding has increased, these grasslands could be made healthy, and at little or no cost.

Grassland soils, so vital to the nation and our cities and agriculture, can only retain water and resist erosion if covered with living plants or litter formed from plant remains. But in the Rocky Mountain West millions of acres are characterized by the sparseness of the grass plants, and more dramatically, by the lack of plant litter between the living plants. Thus, when you measure it, as I have, you find that even on the best managed rangelands, 50 to 95 percent of the soil surface between plants is actually bare and exposed, or at best covered with algae and lichen crusts. This amount of soil exposure inevitably leads to high runoff (flooding) and high soil surface water evaporation (drought).

The types of plants are also important. The grasslands of the Rocky Mountain West are dominated today by woody plants, such as sagebrush, annual grasses that do little to stabilize soil, and a few rest-tolerant perennial grass species of low productivity. It is unnatural to have so few plant species dominate large areas of vastly different soil types, but it is occurring on private, public, and tribal lands and in wilderness areas and national parks.

Why Is So Much Land Deteriorating?

Since plants provide soil cover, let’s look at them first. For simplicity’s sake, we can say there are three broad types of plant in the Rocky Mountain West—evergreen or deciduous woody plants (trees, shrubs, weeds) and grasses. Of these, other than in higher rainfall environments where a full canopy of trees can grow, soil cover is derived primarily from living grass plants and their dead litter, as mentioned. All plants and plant parts follow a simple life cycle—birth, growth, death and decay.

Biological decay is dependent upon billions of microorganisms. If something should block decay, plant parts oxidize and turn gray, leading to the death of most perennial grass species and high fire risks. Evergreen trees have leaves that remain green throughout the year. Deciduous trees have green leaves that grow profusely in spring and summer. In fall these trees withdraw food from their leaves, which change color, and are then cut off and shed—hence the name fall. If the tree could not shed its own leaves, the dead leaves would not decay (too few microorganisms above soil surface level) but would oxidize and smother the tree’s buds the following spring. If the tree could not shed its leaves for a season or two the sheer weight of dead leaf would kill the tree. Fallen leaves decay and are incorporated in the soil on the ground where populations of microorganisms are high.

All perennial grasses grow green stems and leaves in the growing season. In the Rocky Mountain West where moisture is low and there is a long dormant season, the grasses move nutrients out of their leaves and into their roots and bases well before winter. Their dead leaves and stems turn yellow. But where deciduous trees can shed leaves, no grass in the world developed this ability.

The Role of Animals in the Plant Life Cycle

Grasses do not have any mechanism to shed their own stems and leaves simply because they co-evolved with millions of grazing animals. These animals removed dead leaf and stem, ensuring that the growth points, or buds, were exposed to sunlight in the spring. That is why most perennial grasses have their growth points at ground level, below grazing height. The grasses were as dependent on the grazers as the grazers were on them.

The animals, unable to digest grass, had a long-established partnership with microorganisms in their gut, which enabled them to break down a mass of forage into smaller bulk (dung and urine), which could more easily decay. What the animals did not graze they generally trampled to the ground as litter where it would eventually decay. Without the grazing animals to perform this vital function, the decay part of the perennial grass’s life cycle is disrupted. The dead leaves can take decades to break down, by oxidizing and weathering, exposing the plant to an early death by the choking gray leaves. So fire—the severest form of oxidation—is often used to clear the highly flammable material away. When the plant dies, or is kept alive by fire, soil is exposed.

Obviously some perennial grasses developed in sites seldom if ever reached by large grazing animals and they can survive years without leaf removal. They do this by forming branches like a tree with growth points high up on the plant (tobosa), or developing a very sparse structure (gramma or Aristida). These are the types of grasses that now dominate the Rocky Mountain West.

When Did These Grasslands Begin Their Decline?

Over billions of years, despite periodic (in geological terms) major disruptions, the soils and biological communities in the Rocky Mountain West functioned as "wholes"—just as you are a whole person and not merely a colony of blood, skin, bone, and brain cells that can be treated or managed separately. Then suddenly there appeared on the North American landscape some 10,000 to 15,000 years ago, a new creature—the first human predator.

Humans are naturally an omnivorous scavenger and not a predator as you quickly realize if you try to kill a deer with your hands and teeth! But in a geologically short time span we developed into a totally new form of predator using language (organization), fire and spear. Previous predators hunted in packs in open grasslands and their prey protected themselves by bunching into vast herds and dropping their young over short birthing periods.

Predator packs are intimidated by the herd and have to isolate animals to kill them, whereupon many predators feed on one animal. The new human predator did not fear herds and found it easier to kill whole herds (driven over cliffs, into boggy ground or surrounded with fire) than to isolate an animal. Where many pack hunters had fed on one animal, many humans fed on only a few of the animals killed. This new wasteful form of predation, which most animals could not adapt to quickly enough, combined with the fact that humans are omnivorous and can turn to many food sources, proved devastating.

In the few thousand years following the arrival of these skilled, human hunters, most of North America’s megafauna (mainly mammals, over 100 pounds) disappeared due to both hunting, and fire-induced changes to the landscape. European pioneers who described vast herds of bison, deer and antelope were only seeing a remnant of North America’s former glory. Early explorers, like Lewis and Clark, give clues in their journals of the deterioration that was taking place.

Resting Grasslands Is Not Natural

Though I have obviously oversimplified many of my points, I hope you can begin to see how they relate to the situation today. This knowledge was lacking 60 years ago when U.S. government agencies established a number of research plots in the Rocky Mountain West to "prove" that grasslands would recover if rested from livestock and other large grazing animals. Initially such plots respond favorably to no grazing, but as oxidation replaces decay the land deteriorates, as you can see when inspecting the plots today. Those I have inspected and photographed all show serious degradation and little difference between the inside (totally protected) and the outside (animals graze in low numbers). Frequently, research by others has reported little difference between grazed and ungrazed land, which supports what the research plots demonstrate.

Many thousands of years ago when the soils and biological communities in the Rocky Mountain West developed, grasslands were primarily maintained by large grazing animals and very infrequent fire. Today the large herds have been replaced by fewer, widely-scattered, animals, and fire is far more frequent—a trend that began with the arrival of those first human hunters to the Americas.

While a few animals lingering in favored areas, such as riparian zones, is devastating to our river systems, so too is too few animals on the catchment area (or watershed) that feeds those rivers. We can begin to put this right by mimicking what occurred naturally in the Rocky Mountain West prior to the arrival of humans —vast herds moving over equally vast areas—constantly maintaining biological decay and thus healthy grasslands.

Using Livestock as Tools for Land and Wildlife Management

When I first realized we could use livestock as land reclamation tools some 40 years ago, I began working with ranchers in a number of countries to learn how to do that effectively. With their input and many years of trial-and-error effort, we developed a planning process that proved successful and has only become more so as we continue to learn. Plant species not seen in decades have returned, springs have re-appeared and wildlife has grown more plentiful and diverse. Any number of ranchers in the Rocky Mountain West who are using this planning process and managing in this more holistic manner, have received good stewardship awards for their land management. The US Forest Service is currently collaborating with the Savory Center to see if we can establish a national learning site in Idaho where we can encourage environmental organizations as well as livestock operators to work together to reverse the land degradation that is of such concern to all of us. As we have learned on private lands, these public lands can also be managed using livestock as a tool to promote their recovery at low cost. There is no reason why the grasslands of Idaho, or elsewhere in the Rocky Mountain West cannot once again sustain abundant wildlife and healthy rural communities.