(CNN) - From the sinking city of Venice to the mass bleaching of Australia's Great Barrier Reef, climate change is drastically impacting some of the world's most treasured heritage sites.
To date, over 1,000 bucket-list locations have earned a spot on UNESCO's World Heritage list on account of their "outstanding universal value" to humanity.
But, if the world continues to warm -- driven predominately by human activity through greenhouse gas emissions -- many of these landmarks may lose some of those "outstanding" values or even cease to exist at all.
Perhaps the starkest example is Greenland's impressive Ilulissat Icefjord, a World Heritage site where the Sermeq Kujalleq glacier is literally melting before our eyes, partly because of global warming.
"Virtually every World Heritage site has some level of threat from climate change," said Adam Markham, deputy director of the Climate and Energy Program at the Union of Concerned Scientists, a science advocacy NGO based in the United States.
At some locations the threat is obvious and imminent.
Yellowstone National Park in the US, for example, is experiencing shorter winters with less snowfall, warmer rivers, shrinking lakes and wetlands, and longer fire seasons, according to a joint report by the United Nations Environment Programme, UNESCO and the Union of Concerned Scientists.
Scientists estimate that nearly half of the wetlands in the Greater Yellowstone Ecosystem could be lost, and more frequent fires will likely lead to its dense forest becoming a more open woodland, over time.
Elsewhere, El Nño events are warming waters around the Galápagos Islands off the coast of Ecuador and disrupting food supplies on which many Galápagos species rely.
Rising sea levels and higher waves during storms are threatening to topple the mysterious moai statues on remote Rapa Nui -- also known as Easter Island -- in the southeastern Pacific Ocean.
'Fastest growing threat'
One in four natural World Heritage sites is highly threatened by climate change, according to the International Union for Conservation of Nature's (IUCN) global assessment of 241 natural sites.
This trend doubled from 2014 to 2017, according to the report, making climate change the "fastest growing threat."
Rising sea temperatures have affected coral reefs, such as the Aldabra Atoll in the Indian Ocean, the Belize Barrier Reef in the Atlantic and the Great Barrier Reef in Australia, in recent years.
In 2016 and 2017, marine heat waves caused by climate change killed about half of the corals on the Great Barrier Reef, along with many others around the world.
And if climate change doesn't slow down, IUCN predicts more sites will likely suffer in the near future.
Mechtild Rossler, director of the UNESCO World Heritage Centre, said they have been continuously monitoring the effects of climate change on heritage.
"If we cannot protect those sites from these threats -- and they have multiple threats -- how will the future look?" she told CNN.
"The (World Heritage) Convention says you have to identify those unique sites and transmit it to future generations. If we have nothing left to transmit, this is a dramatic situation."
Can we save them?
One solution could be to develop a climate vulnerability index, explained Markham. This would enable countries managing heritage sites to better understand, monitor and address the risk of climate change.
Rossler stressed the need for strategies to adapt to extreme weather events and extreme environments, often tapping into knowledge and traditions of local communities.
For example, in the fragile environment of World Heritage-listed Serra de Tramuntana, in Mallorca, where water resources are scarce, people have successfully revived traditional watering systems, she explained.
"If a site is well managed the chances that it addresses climate change better is high," said Rossler.
But Markham concedes that it might not be possible to protect every site, particularly in less developed parts of the world.
While Markham is optimistic that heritage site managers are considering how to deal with climate change, he is not convinced that national governments are taking the actions needed to slow it down.
With climate change it always comes back to meeting the Paris Agreement goal — that is limiting global warming to significantly less than two degrees, he said.
"We're not on track to do that right now unfortunately," Markham added.
"Without meeting the Paris Agreement we are going to lose a lot of World Heritage sites."
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