Will our beloved waratahs survive climate change?

By Tim Low | March 19, 2018

New research shows that our waratahs can withstand a lot.


Tim Low

Tim Low lives in a state of perpetual surprise at everything wild and alive. His response is to write searching books, Australian Geographic articles and this blog. His book Where Song Began (Penguin, 2014) recently became the first nature book ever to win the Australian Book Industry Award for best general non-fiction. Tim’s newest book is called The New Nature.

NSW’S FLORAL EMBLEM, the waratah (Telopea speciosissima), has a new career in climate change research. In greenhouses and the field, waratahs are helping scientists foresee the future.

When fed extra carbon dioxide in one experiment, young waratahs thrived. This was expected because carbon dioxide is plant fuel, which means many plants should benefit from a high carbon world, unless it brings worse droughts, which it may.

When subjected to high temperatures, waratahs from around Sydney outgrew those from the Blue Mountains. Plants often grow better when temperatures are raised, surprising though that may seem. Over the years scientists have found that eucalypts, banksias, lillypillies and many other trees and shrubs thrive if temperatures are raised a few degrees, provided they have enough water. 

But waratahs in the Blue Mountains endured so much cold during the last ice age they may have lost what it takes to benefit from warming, the researchers suggested. The good news is that these plants weren’t harmed by the heat. 

NSW waratah

(Image Credit: Wikimedia/Rexness)

In the wild this waratah species isn’t found north of Newcastle, but it is grown in southern Queensland for the flower trade, confirming that waratahs can take more warmth than they are used to.

Another experiment saw waratahs, along with other shrubs from around Sydney, planted in woodlands 600 kilometres further north, near Grafton, to see what insects attack them. In a warmer future, insects will spread south, so this experiment was a way to anticipate that. Waratahs themselves will remain around Sydney rather than relocating, because they need sandstone soils.

Most of the plants that were moved to Grafton, including waratahs, had fewer insects chewing and sucking them than they face around Sydney. That is good news for the plants, although the experiment only ran for a year so didn’t prove much.

The research gives hope that waratahs will continue to brighten the bushland around Sydney for a long time yet. The honeyeaters that pollinate them will be pivotal to their success. Waratahs near the coast differ, genetically, from those in the mountains, and birds moving pollen between different stands will ensure that some offspring produced in each location have the best genetic makeup for the climates of the future.