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Breeding Birds of the Platte River Valley

Changes in Habitat Quality

Before settlement, most of the Platte River Valley was poorly drained sedge meadows and marshes. The lowland prairies, which were characterized by big bluestem, dominated the valley. Short- and mid-grass prairies of little bluestem and buffalo grass were the dominant feature on the bluffs and tablelands surrounding the valley. The sod of both the lowland and upland prairies remained intact for thousands of years before the arrival of the settlers. Except for the nomadic grazing of bison (Bison bison) and other native species, and the cultivation of small patches for corn and squash by the Native Americans, there was relatively little disturbance of the prairie. Prairie fires, either intentionally set by Native Americans, or naturally ignited by lightning, periodically swept the prairies, stimulating the growth of native grasses and forbs. For thousands of years the natural process of plant production, litter decomposition and decay, and regrowth of underground and aboveground shoots resulted in the gradual accumulation of a rich topsoil 0.15 m to 0.30 m deep.

Early observers failed to recognize the richness and productivity of these soils. The plains were known as the "Great American Desert" because the soils were thought to be so poor that they could not support forests. In fact, the prevailing theory today is that forests were not prevalent on the plains because of the semi-arid climate and the frequent prairie fires. The numerous woodlots and shelterbelts present today are evidence that the soils in the Platte River Valley are indeed sufficient to support trees.

Once the richness of the valley soils was recognized, cultivation soon began. The development of agricultural lands was promoted by the federal government through the Homestead Act of 1862 and the Timber Claim Act of 1873. The Homestead Act allowed settlers to claim 65 ha if they were willing to cultivate or reside on the land for 5 years. Lands given to the railroads by the federal or State governments were also available for purchase. In Nebraska, the Union Pacific, Burlington, and Chicago and Northwestern railroads sold land to settlers through their land companies. In some circumstances the land companies sponsored agricultural fairs in cities such as Chicago, in which they touted the fertility of the prairie and tried to lure prospective land-buyers into starting a new life on the plains.

Homesteaders in the Platte River Valley faced major obstacles in converting the lowland prairies and wet meadows into productive agricultural lands. The first task was simply to break the sod. The dense grass sod that had developed over thousands of years was not easy to turn with horses and a manual plow. Once the sod was turned, the next step was drainage. Although the soils in the valley are sandy and generally well drained, overflow from the river, high ground water levels when the river level is high, and heavy spring rains contributed to standing water areas each spring over much of the bottomlands adjacent to the Platte. It was often too late to plant crops by the time the bottomlands dried out. For this reason, farmers began draining their land by digging open ditches to carry water to the river channel. The wettest areas and those with rolling topography were difficult to farm, and were generally reserved for pasture or hayland. Most of these reserved lands were located on the bluffs surrounding the river or adjacent to the river channel.

Drainage of river lands has apparently been a slow process, beginning in the 1870's and continuing to the present. Most of the large-scale drainage systems were completed by the 1940's. Since that time, declining river levels in the Platte have allowed some of the formerly very wet prairie lowlands near the river channel to be converted to croplands. Many of these lands, however, were flooded during the 1983 growing season when river flows were at a 40-year sustained peak of over 20,000 cubic feet/sec (CFS) (566 cubic meters/sec.).

Unpredictable rainfall and other natural catastrophic events were also major obstacles to early homesteaders. Many settlers were unable to make a living. Nearly 50% of the original homestead entries, for instance, were never carried through to a final claim (Olson 1966). Until the 1940's and 1950's when widespread use of pesticides began, a farmer could protect his crops from the vagaries of nature only by employing a crop rotation program and selecting hardy varieties. As a protection against drought, irritation was introduced as early as the 1860's. The early irrigation systems used direct diversion of water from the Platte and were limited to areas adjacent to the river channel.

Gravity irrigation began to be widely used in the 1940's, 1950's, and 1960's to irrigate relatively level croplands. In such a system either groundwater is pumped or water is delivered through a canal system to the upper end of a field and allowed to flow with gravity through a furrow to the lower end of the field. Land leveling has been used extensively to allow gravity irritation of fields that formerly were not level. The subsequent development of center-pivot irrigation has eliminated the need for land leveling in many situations, and has allowed conversion of lands near the river channel with fragile soils that would not ordinarily withstand land leveling.

On the tablelands surrounding the Platte River Valley, the soils are better drained than those on the bottomlands, and they are also not affected by changes in river level. For this reason, wetland drainage has not been as extensive for development of cropland on the tablelands. Because land on the tablelands is relatively level, nearly all of the native short-grass prairie has been converted to cropland. Wetland basins or "prairie potholes" on the tablelands are generally the only areas that have escaped conversion to cropland. These basins, which primarily collect spring runoff and precipitation, are particularly prevalent to the south of the Platte and are collectively known as the Rainwater Basins. Although the wetland basins have been difficult to drain, fewer than 10% of the basins present at the time of settlement remain today (Schildman 1981).

Along the North Platte River in western Nebraska, relatively rough topography and the arid climate have prevented conversion of much of the native sandhills prairie to cropland. Most of the cropland in the region is in the relatively flat bottomlands near the channel of the North Platte River. In recent years, center-pivot irrigation technology has sparked the conversion of some upland sandhill prairies to cropland, by providing irrigation lands that formerly received too little rainfall to support most crops. However, the uplands surrounding the North Platte Valley remain much the same as in presettlement times. Intensive grazing in some areas has altered the composition and character of grasslands in the sandhills, but most grasslands along the river are in relatively good range condition.

Cropland and Rangeland Changes

The conversion of prairie to cropland along the Big Bend stretch of the Platte River and along the North Platte River was essentially completed by 1911 (Currier et al. 1985). The amount of rangeland (principally native grassland)in the Big Bend region has fluctuated very little since 1911. Only 38% of the native big bluestem lowland prairie and short-grass upland prairie remained in 1911. Following a slight decline (3%) in rangeland between 1911 and 1939, the amount of rangeland increased to 42% by 1950. This increase is probably in response to the drought years in the 1930's, and most likely represents croplands which were either seeded or allowed to revert to grassland. By 1980, the percentage of rangeland had declined again to 39% of the total land area.

Along the North Platte River, much more of the native grassland was still present in 1911. At that time 83% of the rangeland remained. There was a decline of about 10% in rangeland from 1911 to 1939 and this decline continued through 1950. Between 1950 and 1980, however, the amount of rangeland increased to 79% of the land area along the North Platte River.

Changes in cropland between 1911 and 1980 have been more dramatic than those in rangeland. Although some native grasslands are included in the hayland category, most of the area represents alfalfa production. In the Big Bend region there have been 2 major changes in cropland acreage. First, the amount of hayland has steadily declined from 16% in 1911 to 6% in 1980. This change reflects the shift from raising a mixture of crops and livestock toward raising row crops only. Secondly, the area of land in corn gradually increased from (22%) 1911 to (25%) 1950 and then dramatically increased between 1950 and 1980 to 44% of the land area. This jump in the production of corn has largely been at the expense of a reduction in other crops which declined by 15% between 1950 to 1980. The slight decline (3%) in rangeland in the 1950 to 1980 period may also account for some of the increase in corn acreage. The shift towards corn has resulted in cropland monoculture in many areas adjacent to the Big Bend stretch of the Platte River. In 1980, corn accounted for over 73% of all crop production (including alfalfa). Excluding haylands, 81% of all cropland was planted to corn in 1980. The remaining 19% included wheat, sorghum, soybeans, oats, and barley.

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