While we're on the subject of natural systems management it may be interesting to review earlier posts on the subject. The decline of the bay checkerspot butterfly due to loss of native forbs when its habitat was invaded by Eurasian cool season grasses (see Butterfly Effect), and the more general concerns for "poverty plants" that grow in nutrient poor soils, something that is less common due to the use of fertilizers and emissions from the use of fossil fuels (see Fat and Happy), are aspects of a general issue: you get what you manage for whether you realize what that is or not.

Good range managers pay attention and use the natural inclinations of swards to achieve their purposes. By varying the timing and species mix of sward predators they determine the composition of the sward. A couple of years ago the post Going Dutch noted some work by Dutch researcher Liesbeth Bakker.

The researchers studied a number of plots in the Junner Koeland, a floodplain grassland along the river Overijsselse Vecht. Staatsbosbeheer uses cows to manage the grassland vegetation. However, the numerous rabbits and meadow voles grazing in the area actually consume more grass than the cows.

Rabbits appear to have a preference for grassland that has been grazed by cows. Cows graze away the longer vegetation, leaving shorter grass that is easier for the rabbits to eat. Meadow voles avoid such areas of short grass as this does not provide them with enough cover to escape from their enemies.

Grazing by both cows and rabbits leads to a great diversity of plants. In particular, prostrate herbs such as self-heal, bulbous buttercup and cat's ear thrive in short vegetation, because then they receive enough light to survive. The greatest diversity of plants is found in places where rabbit digging has resulted in bare soil. Therefore, cows ensure that sufficient light reaches the ground, whilst rabbits ensure good germination spots for prostrate herbs.

The large ruminants make habitat for rabbits. The rabbits make habitat for herbs. The nutrient poor subsoil that they pile on the surface when digging their borrows is perfect habitat for "poverty plants". That's their ecosystem role, the niche they exploit, pioneering bare soil resulting from soil disturbance. In time, as they die and decompose, they enrich that soil making it once again suitable for grasses. And so the cycle proceeds. Not stated is that the herbs make habitat for butterflies etc. In a circuitous way cows make rabbits (and gophers and voles etc.), and rabbits make butterflies. There's more.

Finally, Bakker discovered that rabbits are a key factor in determining the extent of shrub cover and whether or not oak seedlings can grow in this. If there are few rabbits, shrub cover can develop in an area grazed by cows and the oak seedlings can root in the shrubs because the shrubs protect the seedlings from the cows. If there are many rabbits, these eat part of the shrub cover and in so doing eliminate the places where oaks can establish.

The vegetation on the Junner Koeland is a mosaic of grassland, shrub cover and oak wood. Such a landscape often contains a large diversity of plants and animals. Management of these natural habitats requires a knowledge of how different grazers affect the ecosystem concerned.

The post Ruminants and Rodents discussed intentional use of grazing to control invasive species.

Rodent populations increase and decrease with the availability of forage. When swards are grazed by ruminants, there is less forage available to support rodent populations. That's how grazers can hurt gophers in the scenario discussed above. But goat grass isn't the only invasive plant rangeland managers battle, woody shrubs can be as bad or worse. In a paper presented to the Ecological Society of America and the Society for Ecological Restoration at their joint 2002 Annual Meeting in Tucson, Arizona, Dennis M. Bramble, University of Utah, noted that ruminants do not generally consume large amounts of brush and woody vegetation, but rodents will consume the roots of these species when other forage is not available.

Range managers can use this interaction to control sward composition and to reduce sward degradation by invasive shrubs. Deferring ruminant grazing in the spring can allow an increase in rodent populations. When the sward is subsequently grazed by ruminants, the large rodent population will switch to eating shrubs. The net result is a reduction of shrubs. It's a balancing act in which the timing of actions matter as much or more than the intensity. In this case both the invasive grass and the invasive shrubs can be controlled by timing grazing pressure, by deferring ruminant grazing in the spring.

Large ruminants are top predators in grasslands and savannas. To the uninformed eye - i.e. the vast majority of politicized pseudo-environmental wankers such as Stanford University biologist Paul Ehrlich (see the butterfly post) - the predation of large ruminants such as cattle is merely destructive. It may help to see how false this is by moving up the food chain to consider top carnivores that prey on ruminants, such as wolves, and their contribution to the health of ecosystems. See Ecology of Fear for a useful discussion of this relationship.

Humans are part of such systems, whether they understand their role or not, and hugely affect even the smallest details by doing things and failing to do things. You are damned if you do and damned if you don't but you can choose your fate. The idea of doing no harm, of withdrawing from natural systems to remove the taint of humans, is ignorant of ecology. You can't withdraw, you can't be pure and harmless. Like rabbits, voles and microbes you harm some things just by being alive but you also help some things. The trick is to see the whole system, your place in it, and make choices. See Aesthetics, Ethics and Ecology for a discussion of this.

What is clear is that the fussy and uninformed sensibilities of pseudo-environmentalists, squicked out by natural systems due to their impoverished urban mind sets, harm ecosystems. This is the most dangerous threat to ecosystems. The views of people like Ehrlich, though he is a biologist with decades of field study, are nonsensical because he can't reconcile reality with his ideology. It isn't that he is the demon and stifling him would make things better, it is that he represents the vast majority of the environmental community. They understand neither the human nor the non-human world, and so fail to be useful contributors to socio-ecological, socio-economic and socio-political systems.

» Circle Jerk from Crumb Trail
See Habitat Management at M&M which gathers several crumbs from the trail to make a larger point. Humans are part of such systems, whether they understand their role or not, and hugely affect even the smallest details by doing......[read more]
Tracked: April 23, 2005 10:14 AM