The United Nations Special Rapporteur on human rights and the environment says Fiji must do more to strengthen environmental protections.
David Boyd also said he was disturbed to hear Fijians were worried about limited civic space for speaking out freely about human rights and environmental problems.
His comments came after an official visit to Fiji which finished on Monday.
Mr Boyd praised Fiji for its global leadership on climate change and urged richer countries to step up financial assistance.
He said the country had introduced several good laws aimed at protecting people from climate change and environmental degradation.
But he said there were serious gaps on the ground, including weak waste and sanitation management, damage from mining activities, inadequate urban and town planning and the degradation of ecosystems.
"I witnessed how these environmental problems interfere with a wide range of human rights, including the rights to life, health, food, housing, water and sanitation, as well as the right to live in a healthy environment," Mr Boyd said in a statement.
The Special Rapporteur will present a detailed report on the visit to the UN Human Rights Council on 20 March.