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November 20, 2013

Land use management affects watershed landscape

Focus in southwestern Ohio, U.S.A.

The watersheds in southwestern Ohio have had huge changes in their landscapes over time. These changes include spectacular increases of 460% in rain-field cropland and fields dedicated to grow pasture, with an estimated 560% increase over a period of 300 years. These changes affected water quantity and quality; they increased quantity at the cost of a significant decrease of quality, by having fertilizer and salts in high concentrations.

In the area of land-use and biodiversity the watershed system had significant changes, since specialized cash grain production took the lead as agricultural system of production, diversity in Preble County, Ohio has dropped, and significant reduction in crop and land-use diversity has been observed from 1934 to 1982. The landscape has become polarized from 1956, reducing fragmentation and concentrating agricultural patches in the upper watershed, forest-patches in the stream gullies and state park land in the lower.

Preble County Ohio
 

Preble County Ohio

The causes of these changes can be traced to global trends, such as the intensification of grain-crop production, which took place mainly in the upper watershed. An observed decrease of productivity and/or legal constrains to the use of some patches of land, which became driving forces in the lower watershed and stream gullies, leaving the time and space needed to follow the path of forest succession. During the last century social needs have changed. In recent decades, demand for recreational areas has grown and this has led to an increment in the forest areas.

This is clearly a complex issue; it involves several areas of work such as:
Health issues in the area of the safety of drinking water that comes from the streams.
A rise of the water tables, which results in water logging.

Long term productivity of the area challenged by the loss of top-soil and the high
concentration of salts and fertilizer diluted in the water used for irrigation.
Loss of aesthetic value of the rural landscape due to the degradation of the ecosystem, with the consequential loss in revenue associated with recreational activities.

Unfortunately there are long time lags between land use change and water resource impacts. This condition plays against the pledge to have better land use management, or setting up remediation programs.

Change in land use management is promoted by different concepts, programs and social trends. Identifying them is an important task towards better management of this resource and the achievement of sustainability for the watershed. It has been reported that in this and other areas around the US, the main forces driving change are technological changes, family traditions, changes in population density, land value, land ownership turnover, general standing of the rural economy, government programs and financial support of new and sustainable land use management.

Together, these factors add up to a healthier environment, which is sustainable and provides economic value for its recreational assets. To create a successful program for the sustainable management of the watershed system, these are the tools and concepts where our efforts should be focused.

land_managment
 

Land cover data documents how much of a region is covered by forests, wetlands, impervious surfaces, agriculture, and other land and water types The National Ocean Service

**Harkers Run is a stream which drains into Four Mile Creek in Preble County, Ohio, U.S.A.

References
Scanlon, B. R., Jolly, I., Sophocleous, M., and Zhang, L. 2007. Global impacts of conversions from natural to agricultural ecosystems on water resources: Quantity versus quality. Water Resources Research 43:W03437+.

Medley, K. E., Okey, B. W., Barrett, G. W., Lucas, M. F., and Renwick, W. H. 1995. Landscape change with agricultural intensification in a rural watershed, southwestern ohio, U.S.A. Landscape Ecology 10:161+.

Kimberly E. Medley, Christine M. Pobocik, and Brian W. Okey. 2003. Historical Changes in Forest Cover and Land Ownership in a Midwestern U.S. Landscape. Annals of the Association of American Geographers 93:104+

Posted by Mark Contorno

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