APPLIED ECOLOGY 



329 



that artificial fishponds can be a profitable investment. The eco- 

 logical problems to be solved for such ponds include sizes and 

 depths for different climates, drainage, amount of available water 

 and necessary aeration, rate of silting under different conditions, 

 fish food relations, kinds and amounts of fertilizer necessary, kinds 

 of fish, and rate of stocking. Marshes might be retained and im- 



FlG. 175. A half-acre farm pond in West Virginia of the type being wide- 

 ly installed for food production and recreation.— U. S. Soil Conservation 

 Service. 



proved for muskrat production, but, again, the practical problems, 

 largely ecological, have not been sufficiently explored. Stream 

 margins create other land-use problems. Usually they are grazed, 

 and, as a result, they erode. The species that would appear under 

 protection should be known, as well as the most desirable species 

 for checking erosion. In many sections, planted hedges and field 

 border plantings are being recommended on the unproductive 

 margins of fields to reduce erosion and provide cover for wildlife. 

 The ecology of the planted species must be known as well as its 

 effects on the crop beside it. Also the ecology of the insects, birds, 

 and mammals of these margins must be known. Are they desirable, 

 beneficial, or are they harmful to desirable species? 



Land Management.— The operations by which land is prepared 

 for crops, their planting, harvest, and use are known as land man- 

 agement. For greatest efficiency, good land management must 

 parallel good land use. These are arts but, today, arts requiring all 



