Imagine you want to monitor changes in plant diversity, to see whether diversity is increasing or decreasing over time. What spatial scale would you study?
Would you search for changes at the global scale, or at continental, regional or local scales? More importantly, would you expect to see the same trend or different trends if you examined changes at many scales?
At the global scale, biological diversity on Planet Earth is on the skids. Thousands of species face extinction and over a thousand hectares of forest are cleared every hour. Species diversity is falling because species are going extinct faster than new species can evolve. And we’re causing it.
Do you think you can estimate the cover of plants as well as the experts?
I’m sure you can. When we all put our minds to it, we can do it really well.
A few years ago, sixteen experienced botanists were asked to estimate the cover of spinifex (Triodia) tussocks in a patch of Mallee. Each botanist was asked to estimate the cover to the closest 10% – e.g. 20%, 30%, 70% and so on – so they didn’t have to get it exactly right. Each did it privately and didn’t know what the others were going to say.
How variable do you think their estimates were? For example, if the real cover of spinifex was 35%, what do you think the lowest and highest estimate was? Would most estimates have been 30% or 40%, or would the range have been much wider, or perhaps narrower?
Don’t read on. Stop and guess. If the real cover was 35%, what do you think the lowest and highest estimate was?
Hans Heysen’s famous painting, Droving into the Light. Art Gallery of Western Australia.
Picture a gorgeous woodland in the early 1800s. What do you see? Majestic gum trees with bent old boughs, golden grasses, a mob of sheep or kangaroos, and a forested hill in the distance? The luminous landscape of a Hans Heysen painting, perhaps.
It’s an iconic Aussie landscape. But something’s missing. The trees are wrong. Or at least, they aren’t all there. Continue reading →
Drought-killed Acacia, Callitris and Eucalyptus saplings at Mt Pilot in north-east Victoria. The tall dead trees in the background were killed by an earlier fire.
In 2010, Craig Allen and colleagues published ‘the first global assessment of recent tree mortality attributed to drought and heat stress’ (Allen et al. 2010). In this fantastic paper, the authors collated examples of tree die-off (or mortality) from around the world and – in a very long sentence – they concluded:
… studies compiled here suggest that at least some of the world’s forested ecosystems already may be responding to climate change, and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited.
Given that pessimistic prognosis, it’s worth asking; how are trees faring here, in our own backyard? Continue reading →
Red Gum seedlings regenerate after the Big Wet flood waters recede
In an earlier blog I asked, ‘What impact did the big wet of 2010-2011 have on native vegetation? Did heavy rains promote lots of regeneration in some areas, but not others? Or did nothing much happen at all?’ In response, many readers submitted lots of great observations from across south-east Australia.
I collated the observations of wetland and rivers and grasses, herbs and weeds in earlier posts. But what happened to trees and shrubs? Did the heavy rains trigger lots of regeneration or nothing much at all? Initially I thought there’d be lots of regeneration in most places but, as it turned out, readers noted abundant regeneration in some areas but none in others. What caused these patterns? Read on to see what everybody found…. Continue reading →
How did the Big Wet years of 2010-2011 affect your local vegetation? Many readers sent in their observations when I asked this question in an earlier blog. Last week I summarized all of the observations from wetlands and floodplains. In the post below I summarize observations about grasses, herbs and weeds from the ‘dry’ hills and plains. Continue reading →
In July, I invited readers to send in observations about how the ‘Big Wet’ years of 2010-2011 affected native vegetation in their local area. Many readers submitted fantastic comments, which I promised to synthesize. I’ve divided the observations into a series of topics which I’ll post in the next few weeks as there were far too many comments for one blog post.
This week, I’ve pooled together all of the observations from the wettest of the wet areas, from floodplains, rivers and wetlands. Continue reading →