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20 Jul 2020

Trees – battered and burnt, but resilient.

The ecosystems of Australia are amazing – amongst the most biodiverse on the planet with species that have evolved in isolation for millions of years. Over 85% of Australian plants are endemic to Australia – meaning they are found nowhere else on Earth.

Dr Brett Summerell Director Research & Chief Botanist


The plants in these ecosystems moderate our climate, protect and provide habitat for a myriad of creatures and are critically important in cycling nutrients in Earth’s ecosystems. 

The fire season in the summer of 2019/2020 saw devastating impacts on trees and the whole natural world across Australia. The extent of the bushfires was of a scale that was and still is very difficult to comprehend. 

Over the past 18 months I was regularly asked: What has the impact on plants been? Burnt landscapes of immense size, are of course mainly made up of burnt plants – trees and the understorey species that comprise those rich and beautiful ecosystems. How many plants have been killed?

It is difficult to estimate the number of plants impacted by the fire. 

Published tree densities in different types of ecosystems range from 500 – 1,200 trees per hectare. And if we multiply this by the area burnt (12.6 million hectares) with an assumption that 60% was natural ecosystems this could give 3.8 – 9 billion trees impacted; with probably just as many understorey species also affected. 

The impact on understorey species is usually much more dramatic, and final, as these species are more likely to be burnt completely. Fortunately, in many ecosystems we have seen encouraging signs of recovery – species regenerating from epicormic buds, new seedlings germinating from the soil from the store of seed and in some cases plants growing that haven’t been observed for years or even decades. We have been lucky in that rainfall in many regions of New South Wales has been above average and this has promoted growth of many species. My expectation will be that the coming spring will be spectacular in many of our bushland areas – hopefully we will be able to get out to see this!   

We have been monitoring the recovery of plants in bushfire affected areas across New South Wales – trying to understand what survived and those species or ecosystems that are struggling to recover. Our seed collectors have been extremely busy to ensure that as many species that are able to produce seeds have been collected – leaving behind enough to ensure regeneration – so that we can protect those species in the long term.

We need trees - the most critical thing trees do is store carbon – taking in carbon dioxide during photosynthesis and expelling oxygen for us and all other organisms to breathe. 
 

The most critical thing we can do right now is to protect existing trees in all our landscapes whether urban environments, rural landscapes or in the bush – especially in those areas that were burnt during the fires. If you get the chance to get out into the bush make sure you go in clean – a quick spray of methylated spirits on your boots will kill any disease causing organisms – and stay on the existing paths. The trees in these ecosystems have already trapped huge amounts of greenhouse gases and will continue to do so. We all need to be advocates for the preservation of these amazing living organisms that contribute in so many ways to our existence.

Learn more

In this episode of Branch Out you'll discover the amazing fire survival mechanisms of plants, the recovery efforts to save some species from extinction and the potential long-term effects and future outlook of our fire season. Or hear an update from Dr Brett Summerell during a recent visit to the Blue Mountains Botanic Garden Mount Tomah in the video below.

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