What Is The Measure?

I live in rural central Pennsylvania. There is good farming land in the limestone valleys. Forty years ago thick hedgerows lined the fields, connecting to the forested mountain ridges. All manner of birds and small mammals lived amongst the trees, shrubs, forbs and grasses in the hedgerow habitat. On a Spring evening one could hear the Whippoorwills sing. No more. Today---the hedgerows are nearly gone. How many extra bushels of corn or soybeans are added to yeilds by eradicating the hedgerow's shade? How many 'edge' species have had to find homes elsewhere? What was lost? What was gained? And what exactly---is the measure?