The first lighthouse on Green Island began operation on July 1, 1875. Twelve metres tall, constructed of granite, it was built to guide ships through the Sulphur Channel and into Victoria Harbour. Two cross-shaped openings in its walls provided ventilation and lighting — the same design used at the Cape Collinson Lighthouse at Siu Sai Wan. That first lighthouse was eventually retired in 1905, when a second, larger structure was built to carry a more powerful lens relocated from the Cape D'Aguilar Lighthouse. The original building proved too small for the new optics. Both lighthouses, along with the former European quarters and a keeper's house, were declared monuments in 2008. They had already been listed as Grade II historic buildings. The lighthouse compound on the hill is one of the more quietly significant pieces of colonial-era infrastructure still standing in Hong Kong.

Green Island is densely covered with woodland and tall scrub. Surveys have recorded 150 plant species on the island, along with a large variety of butterfly species. More unusual: an ant species not previously recorded anywhere else in Hong Kong was found here. The reef egret and white-bellied sea eagle have both been spotted on the island — the reef egret is locally rare, a bird that works tidal rocks for fish and is easily disturbed. The island's isolation from urban development has allowed a small ecological community to persist within a few kilometres of one of the world's most densely populated cities. Little Green Island, an uninhabited islet to the east, adds a buffer zone. Neither island has been significantly developed, and the Green Island Reception Centre and a police station on the east coast remain the extent of permanent occupation.

The aviation role of Green Island is specific and practical. Victoria Harbour is narrow, and the volume of helicopter and light aircraft traffic operating in and out of it is substantial — the harbour hosts helipads, the Macau ferry crossings, and private aviation activity. Air traffic control requires all local traffic to report overhead Green Island before entering the harbour. When the harbour is particularly busy, Green Island serves as a holding point: aircraft orbit until cleared to proceed. This is an unusual distinction for a nearly uninhabited island. It has no runway, no tower of its own, but its position at the western mouth of the harbour makes it an indispensable waypoint.

In the 1990s, the Hong Kong Government proposed reclaiming approximately 181 hectares of the Sulphur Channel to house a population of 103,465 people. The scheme, tied to a coastal highway from Kennedy Town to Aberdeen and a fourth cross-harbour tunnel to a proposed container port at North Lantau, would have transformed the waters around Green Island entirely. Environmental groups opposed the plan. The opposition held. The proposal was shelved. The channel remains open water, the island remains forested, and the lighthouse still blinks across the harbour approach at night — unchanged since the reclamation plan was quietly abandoned.