The Critical Trends Assessment Program (CTAP) monitors the biological condition of Illinois' forests, wetlands, and grasslands. This program is supported by the Illinois Department of Natural Resources, is the first statewide comprehensive assessment of its kind. Since 1997, CTAP scientists have collected plant, bird, and arthropod data at more than 600 randomly selected sites on both public and private lands. The data we collect and analyze are used to help numerous stakeholders understand the past and current condition of Illinois' ecosystems.