The pilot was participating in a glider contest where about 50 other gliders would also be flying. The surrounding terrain had areas of clear-cut, (stumps and scrub brush) standing trees, isolated buildings, rural roads, farm fields, and a residential area near the airport. The terrain was flat, and the gliders were being launched about every minute. The pilot’s glider was the seventh glider launched. The plan was for each glider to be towed to an altitude of 2,000 ft agl before release. The tow path resulted in the pilot flying north-east, parallel to the runway, opposite the direction of takeoff. The pilot released about 100’ lower as he felt a significant surge of upward moving air (lift) and wanted to exploit it to gain altitude for the balance of the flight. When he felt the lift, he cleared the area and released to the right, followed by an immediate 270° left turn to search for the lift, however he was unable to find it, and proceeded to search over ground that appeared favorable for the generation of thermals. Finding none after circling five times, he proceeded to head south-southwest back towards the airport in case he would need to land. At this time, he was at approximately 1,000 agl and 1.8 miles from the airport. About 1.7 miles from the airport, he encountered significant sinking air, which reduced his altitude to approximately 600 ft when he was about 1.5 miles from the airport. He believed that he probably would not make it to the airport to land safely. He then encountered a strong thermal and tried to circle and catch it as he believed that it would likely be his only chance to save the flight. He then circled three times, but only lost more altitude. He then identified a small field to attempt to land in. The field was surrounded by trees and was only a 500-to-600-foot long. He tried to land on the field from the south as low and slow as possible but was not able to reach the field before impacting the trees at the northern edge, which resulted in substantial damage to the glider. In a summary statement, the pilot further described the factors that he believed contributed to the accident. He stated in part, “There were a combination of stressful factors which contributed to this accident, but it all got down to not staying with the decision to get to the airport after encountering the big sinking air. I probably could have made it to the airport had I just kept going, but the rapid loss of altitude was so alarming that my decision-making switched to survival mode.”