Major problems that face the Tallgrass Prairies
by James C. Trager
Dear Kunal Shah:
Your letter inquiring about prairies came to me through Glenn Pollock
and a network of people interested in discussing prairies on the
internet, to which I am also forwarding this letter.
I will focus my comments on the tallgrass prairie, or roughly the
eastern third of the grassland biome in North America. The major
problem facing the tallgrass ecosystem is that it is no longer an
integral ecosystem, but merely a far-flung array of remnants,
tiny polygonous dots on the map of the former tallgrass region.
These small areas have lost many species once occurring on them,
back when they were surrounded by more prairie area, because in
general, small habitat areas harbor fewer microhabitat types than
larger areas and thus support fewer total species. The loss of
prairie area is especially hard on prairie-specialist vertebrates,
such as grassland mammals, birds and reptiles.
If loss of total area were the only problem, the losses of species
would be less severe. But...
1) Many prairie areas have a history of overgrazing, leading to
compacted and eroded soils, and vegetation with a disproportionate
amount of species of the kinds less palatable to livestock (and
wildlife), and loss of palatable types.
2) Grazing areas have often been subject to spraying with herbicides
to kill broadleaf plants in the misguided belief that pure grass
stands make better forage for cattle. This greatly reduces the plant
biodiversity of the prairie, which though dominated by grasses,
contains literally hundreds of other, non-grass species. Speaking of
pesticides, insecticide drift from adjacent crop fields has
probably caused losses of pollinators and other prairie insects,
though this is not well documented.
3) Native wildlife, especially predators and large native grazers,
has been displaced, shot or poisoned to make way for domestic grazing
4) Most remnant prairies are on poorer, stonier soils, which
couldn't be plowed. These less fertile sites are not fully
representative of the prairies on better soils with their lusher
growth and greater biodiversity. Almost all good-soil prairie land
(the great majority of what once occurred) has been converted to corn
and soybean agriculture.
5) Most wet prairie areas (as much as 1/4 of the total prairie area
of the vast prairies of what is now Illinois and Iowa), were drained
and converted to agriculture, leading to the near extinction of this
distinct type of prairie community.
6) Many of the existing prairie remnants have been hayed annually
over a period of decades. This removal of plant life, cut at the peak
of growth each year, has lead to losses of plant species flowering
and setting seed at that time of year, and to loss of insects, birds,
etc. depending on the plants for habitat and food. Haying annually
over a period of many years has also led to chronic loss of nutrients
from the system.
7) And, while native prairie species are increasingly under pressure
from these forces, they are also under pressure from growing
(sometimes exploding) populations of invasive plant and animals.
These are species spreading from human-planted areas such as
"improved" pastures, roadsides, crop fields and gardens. These
creatures, especially certain plants, arrive here through human
activity and are often completely free of the natural enemies that
control their populations in their "homeland". So, they can increase
at astonishing rates, displacing native plants and all the life that
depends on them.
8) And finally, since prairies originally depended on a combination
of grazing by wildlife, periodic drought, and (especially) fires from
natural or human (native American) causes for their existence, even
some of the least damaged prairie sites are undergoing change to
relatively low-diversity second-growth forests. Let go long enough,
the prairie plants and animals may be lost completely from the site.
Meanwhile, the development of a diverse and fully-developed forest
system may take hundreds of years.
NOTE: A few words about the benefits of fire...
Haying, or preferably mowing, can keep the invading trees out of a
prairie site, but the specific effects of periodic, dormant-season
(winter) fire, including increased and early warming of the soil in
spring, rapid release of nutrients from the burned plant material,
direct heating of seeds in soil which stimulates germination, and
release of non-nutrient combustion products into the soil which
trigger plant growth (demonstrated for grasslands in Australia, but
not yet for North America) cannot be duplicated by any other process.
To stay healthy, prairies need fire from time to time, but this
conflicts with safety and clean air concerns of the hear by human
9) The latter, namely we, are the source of all the above problems.
But, it is also true that it is enlightened people who can save
what's left of the prairie, and hopefully increase it, at least a
little, through ecological restoration and prairie re-planting, and
through public education about the beauty and value of prairies.
BEST OF SUCCESS ON YOUR STUDY OF THE GRASSLAND BIOME.
James C. Trager
P.O. Box 38
Gray Summit MO 63039