Forty years of landscape change in Attwater's Prairie Chicken habitat within the Coastal Prairie of Texas

Abstract

The Gulf Coastal Prairie is one of the most intensively utilized natural region,-in Texas. Agricultural development, urbanization, mining (oil and natural gas) and their infrastructure have served as agents of prairie destruction and fragmentation. Two areas with continued Attwater's prairie chicken presence within the Coastal Prairie were selected to study long-term landscape change. The northern area represents an agricultural dominated area managed for prairie chickens. The southern area represents an agricultural/mining area without any management plan. Aerial photographs acquired at intervals from 1952 to 1990 were used to determine land cover. Photographs were classified, digitized and entered into a geographic information system for comparison and analysis. The north study area is comprised of 56,000 ha and centered on the 3,240 ha Attwater Prairie Chicken National Wildlife Refuge. Aerial photographs from 1952, 1964, 1982, and 1990 were used. Potential prairie chicken habitat decreased from an initial 29,343 ha to 9,355 ha in 1990. The number of prairie patches increased from 5 to 21 while mean patch size decreased from 5,868 ha to 446 ha over the same period. Coarse landscape statistics indicated area and perimeter were the best tests for change. Prairie chicken population declined by 89% over the 40 years. Mapped lekking sites from 1979 to 1992 declined from 34 to 8. Mean distance to nearest leks ranged from a minimum of 1, 1 14 m to 2,821 m while sites were increasingly aggregated in the landscape. The south study area is comprised of 161,000 ha of cropland, rangeland and oil production fields. Aerial photographs from 19 5 5, 1969, 198 1, and 1990 were used. Potential prairie chicken habitat decreased from an initial 102,301 ha to 54,972 ha in 1990. The number of prairie patches increased from 4 to 10 as mean patch size decreased from 25,575 ha to 5,497 ha for the same period. Coarse landscape statistics did not suggest any metric which showed a significant change. Prairie chicken population declined by 94% over 35 years. Mapped lekking sites from 1979 to 1992 varied from 15 to 32. Prairie chickens abandoned portions of the landscape during this time, reducing mean distance to nearest lekking site from 3,23 5 m to 1, 3 67 m in 1992. The remaining lekking sites were highly aggregated in the landscape in 1992.