They found that if the planet heated by over 3C - as current trajectories put it on track to - then a third of endemic species living on land, and almost half of endemic species living in the sea, face extinction.
On mountains, 84 per cent of endemic animals and plants faced extinction at these temperatures, while on islands that number rises to 100 per cent.
Overall, 92 per cent of land-based endemic species and 95 per cent of marine endemics faced bad consequences, such as a reduction in numbers, at 3C.
Around the world, threatened by climate change included all species of lemur, unique to Madagascar; the blue crane, national bird of South Africa; and the snow leopard, one of the most recognisable animals of the Himalayas.
As for New Zealand, Costello said the country's large size and topographic variation - allowing species to move uphill to find cooler conditions - might enable them to adapt to a warmer climate.
"In addition, while climate change is happening in New Zealand, it is not as severe as happening near the equator where many species are already at their temperature limits, or in the high latitudes of the northern hemisphere," he said.
"Thus, if native species can shift their distribution in New Zealand this will allow them to survive."
Costello however added that a warmed climate means more pressure from introduced pests - those already here, and potentially other future invaders.
"We need to protect native natural habitat at a national scale, and especially on land, provide natural corridors that allow species to disperse across heavily urbanised and farmed landscapes."
Ultimately, the study found that endemic species were 2.7 times more likely to go extinct with unchecked temperature increases than species that were widespread, because they are only found in one place.
If climate change altered the habitat where they lived, they were gone from the face of the Earth.
Places like the Caribbean islands, Madagascar, and Sri Lanka could see most of their endemic plants becoming extinct as soon as 2050.
The tropics were especially vulnerable, with more than 60 per cent of tropical endemic species facing extinction due to climate change alone.
But if nations succeeded in meeting the Paris Agreement's most ambitious aspiration - no more than 1.5C of heating - just 2 per cent of endemic land and sea species would be lost.
Those figures more than doubled at 2C, and, if the warming hit 3C, they jumped to 20 per cent and 32 per cent endemic land and sea species, respectively.
"Countries need to fulfil their promises to protect nature and use nature in an environmentally sustainable way, especially in areas with high numbers of endemic species," Costello said.
"Without reducing greenhouse gas emissions globally, climate change-driven extinctions will happen."
The study, led by Dr Stella Manes of the Federal University of Rio de Janeiro, is published in the journal Biological Conservation.
