Government advisers yesterday expressed scepticism over the Airport Authority's environmental report on its proposed third runway, saying it was full of highly speculative assumptions and "wishful thinking". The concerns came from members of a subcommittee of the Advisory Council on the Environment, in the first of three days of meetings. The Environmental Protection Department is to make a decision on whether to approve the report later this year, based on input from the advisory council. The advisers' dismissed the assumption in the report that Chinese white dolphins, which would be displaced during construction, would come back to a new 2,400 hectare marine park. The park, which would connect the existing Sha Chau and Lung Kwu Chau Marine Park with the planned Brothers Islands Marine Park, was proposed as a key mitigating measure in the authority's assessment. However, it will not be put in place until the project's completion, slated for 2023. Council member Dr Hung Wing-tat said the authority needed to present hard data to show how many Chinese white dolphins would return to the area once the park was designated. Watch: SCMP took a look at Hong Kong's pink dolphin habitat "You speak of creating a fairytale … a paradise … How can you make sure that in seven years' [from the start of construction of the proposed third runway] there will be peace in that area for the dolphins?" Hung asked. He said the case would set a bad precedent for conservation measures associated with future projects. Professor Chau Kwai-cheong urged the authority to "think outside the box" and consider offsite compensation measures, such as a marine park on Lantau Island's southwest side, in addition to onsite ones. "It is wishful thinking to think the dolphins would just come back," he said. Consultants to the authority said scientists "did not work on guarantees" but that dolphins would return to well-protected areas. They said the marine park was necessary. Dr Thomas Jefferson, a consultant for the authority, said dolphin numbers would fall initially but rebound later, as they had after the construction of Chek Lap Kok airport in the 1990s. Council member Dr Gary Ades said this was like comparing "a grape and an apple" as land reclamation and habitat loss took place on a much smaller scale back then. The authority yesterday added four additional mitigating measures, including a cap on high-speed ferries from the airport's SkyPier at its current level of 99 per day. The members also complained about a lack of worst-case scenario planning and poor predictions on air quality and aircraft noise impacts. Hung also questioned the report's contention that airlines would replace their fleets with lower-emission, quieter aircraft, and cross-border air quality reduction targets would be met. The airport operator had said the runway would bring not just minimal air pollution but even improvement to some areas. It claimed fewer residents would be exposed to aircraft noise if the operation moved closer to Tuen Mun and Tsuen Wan. Laurent Delarue, the authority's air traffic forecast consultant, defended the report, saying they had done interviews and surveyed top airlines operating in Hong Kong and found many of them had plans to upgrade their gradually ageing fleets.