A series of biennial reports from the U.S. National Research Council have reviewed the progress of CERP. The fourth report in the series, released in 2012, found that little progress has been made in restoring the core of the remaining Everglades ecosystem; instead, most project construction so far has occurred along its periphery.[181] The report noted that to reverse ongoing ecosystem declines, it will be necessary to expedite restoration projects that target the central Everglades, and to improve both the quality and quantity of the water in the ecosystem.[182] To better understand the potential implications of the current slow pace of progress, the report assessed the current status of ten Everglades ecosystem attributes, including phosphorus loads, peat depth, and populations of snail kites, birds of prey that are endangered in South Florida. Most attributes received grades ranging from C (degraded) to D (significantly degraded), but the snail kite received a grade of F (near irreversible damage). The report also assessed the future trajectory of each ecosystem attribute under three restoration scenarios: improved water quality, improved hydrology, and improvements to both water quality and hydrology, which helped highlight the urgency of restoration actions to benefit a wide range of ecosystem attributes and demonstrate the cost of inaction.[182] Overall, the report concluded that substantial near-term progress to address both water quality and hydrology in the central Everglades is needed to reverse ongoing degradation before it is too late.