The outlook for Australia’s Great Barrier Reef looks grim, with many of the threats to its environmental health worsening over the past five years and expected to deteriorate further as climate change intensifies, two major reviews have found.

In worrying signs for the future of the world heritage site, two reports released by the federal government on Tuesday have warned the reef is under significant stress.

The first report is a five-yearly outlook report by the Great Barrier Reef Marine Park Authority, the agency that oversees the reef’s marine parks.

The second is a strategic assessment prepared by the federal and Queensland governments as part of a request by the United Nations world heritage body to have the site better looked after.

Broadly, they find that the damage caused to key sections of the reef from climate change, poor water quality, some fishing practices and coastal development has worsened.

These threats were exacerbated by a series of storms, cyclones and floods in the past five years.

While values that make the reef a world heritage site remained “largely intact”, the health of inner reefs in the southern two-thirds of the region had been found to have “declined significantly”.

In the less developed northern and outer regions of the reef, water quality and ecosystems were still considered to be in good condition.

In both reports, climate change was found to be the most serious threat to the reef.

The outlook report said climate change had already altered the Great Barrier Reef’s ecosystem, with its effects compounding other threats.

The extent of damage that climate change would cause to the reef would depend on the strength of international action to cut greenhouse gases that were warming the planet, the outlook report said.

‘‘Climate change is already affecting the reef and is likely to have far-reaching consequences in the decades to come,’’ the report found.

‘‘Sea temperatures are on the rise and this trend is expected to continue, leading to an increased risk of mass coral bleaching; gradual ocean acidification will increasingly restrict coral growth and survival; and there are likely to be more intense weather events.’’

The strategic assessment said, while the reef remained one of the most resilient tropical marine ecosystems in the world, the combination of threats was diminishing the reef’s ability to recover from disturbances, such as coral bleaching.

“Without additional management intervention, there is a high risk of further declines in the condition of biodiversity and heritage values and the community benefits they support,” the report said.

It was also found that the development of new ports on the reef’s coast, a key battle between conservationists and industry, also had significant impacts on key inshore regions.

But the threat was more localised than other widespread concerns such as pollution run-off from farms. The reports point to some areas of improvement, especially measurably lower levels of pollution run-off into the reef’s waters. But the benefits of these gains would take many years to be seen.

Australia’s Environment Minister Greg Hunt said the reports reinforced that there were no quick fixes to the reef’s problems and it would take time to turn around its overall health.

He told Fairfax Media the science of the reports showed the main impact in recent decades had been poor water quality and the invasive starfish species the crown-of-thorns.

‘‘We can make massive progress if we really hit the water quality issue hard. But you have to deal over the medium term with climate change,’’ he said.

He said he was increasingly confident a new global agreement to address climate change would be signed by countries at a meeting in Paris next year.

Hunt pointed to the government’s $40 million reef trust, focusing on water quality problems and coastal habitats, as a key step.

Combined, the Queensland and federal government have committed A$180 million to reef programmes.

But WWF Australia chief executive Dermot O’Gorman said it was time to invest billions, not millions, of dollars in cutting pollution and repairing the degrading ecosystems of the reef.

WWF also wants a ban of the dumping of dredging sludge in the world heritage area as part of new port developments, and for the federal government to retain oversight of environmental approvals for developments affecting the reef instead of handing it to the state government.

The strategic assessment said action at local, state and federal levels, combined with international action on climate change, was “vital” to protecting the reef’s future.

Work in the southern two-thirds of the reef would have to focus on reversing damage.

The report called for five new measures to strengthen the management of the reef, including a reef recovery programmes to restore damaged sites, and improved monitoring and reporting.

But it contained few specific details of how the government should halt the damage done to the reef from climate change, land-based run-off and activities such as dredging and shipping.

Hunt said the five new plans would be developed over the next 18 months.

The Australian Marine Conservation Society said the report was more a “plan for a plan” rather than a concrete presentation of what needed to be done to reverse a serious decline in the reef’s health.

“We’re still seeing approvals of dredging, dumping – nothing concrete that’s going to turn it around,” Great Barrier Reef campaigner Lissa Schindler said.