I came across this most informative article about butterfly habitat. The principles involved can be used in relation to bird habitat, too.
It is apparent from the article that no matter how careful we are in our revegetation & ecological restoration efforts we'll never be able to replicate precisely what Nature has produced. So the over-riding message for me is how important it is to preserve the natural habitat that exists. My admiration for Nature has, in fact, gone up another notch or two or three. Anway, read on: http://www.iffa.org.au/butterflies-and-habitat-restoration-critical-commentary
That is a good article, it emphasises the extent of our ignorance of the natural world and it's complexity.
"Melbourne is probably very similar to the City of Davis, California, where non-indigenous food plants, both cultivated and naturalised are very important for the diverse, highly valued butterfly fauna, so much so that the objectives of butterfly conservationists conflict with those of plant-focused restorationists and weed controllers (Shapiro 2002)."
I think this could be applied equally to birds. I doubt whether restoring a semblance of original vegetation is of great benefit to bird populations. Better to restore the fertility of the system without worrying so much about what grew there before, if you want to boost bird numbers and diversity. But if you want to restore the original plant community as much as you can, you may have to tolerate lower numbers of fauna such as birds and insects.
An interesting article that illustrates how many different factors might come into play in creating desirable habitat for (various critters including birds). There's probably a good argument for a mixture of original and other "support" vegetation. The proportion of that mix is far too involved a question for a simpleton like me.
Hi Greg. I would have thought the "experiment" with non-native vegetation communities as alternatives to the native vegetation communities had been tried with disastrous results as far as biodiversity is concerned. Native vegetation clearance has, in fact, long been recognised as a major factor in bird species decline.
There is certainly an argument for the retention of non-native vegetation where it supports native wildlife in the absence of native vegetation. E.g, black berries supporting red-browed firetails & superb fairy wrens. Hence it's important to retain this vegetation while re-establishing native vegetation. However, once the native vegetation is sufficiently mature to support the bird numbers it's time to remove the non-native vegetation. I guess this notion is relevant to your comment, Night Parrot, about retention of "other" support vegetation.
Greg, I'm aware that you've previously promoted increasing soil fertility as a way of increasing biodiversity but I'm still struggling to see the connection between soil fertility & biodiversity in Australia. Can you clarify this for me, please?
I read a study years ago comparing invertebrate diversity in a pine forest and nearby native vegetation. The author was surprised to find more diversity in the leaf litter of the pine plantation than the native bush. Now no-one prefers pine plantations to native bush, but the study illustrated how easy it is to jump to conclusions. As I said before, soil where the native vegetation has been cleared for grazing or cultivation has been shown to have reduced soil fertility, and it takes many decades for the fertility to return once the farming stops and the native vegetation returns. All life ultimately depends on the soil fertility, and less fertile soil ultimately means less biomass.
When it comes to bird diversity, as the article you linked to says the issue is too complex for us to understand. Is there any study which has compared revegetation using indigenous species to using exotic species? I doubt it. Of course revegetation is better than the monoculture of modern agriculture, that isn't the point, though the pine forest study showed even that can be contentious.
If you can't see a link between soil fertility and biomass leading to greater diversity for birds, then I doubt I can convince you. I would like to caution against wishful thinking in these things. We would all like to think indigenous species is the best thing to encourage native birds, but is it really so? I can't see any evidence for that.
This is probably an "argument" no one can win. No doubt increased biomass provides a greater food supply and, through increased populations (of birds), gives potential for greater diversity. Woko would probably say provided its the right type of biomass and the right diversity. No doubt we could all provide examples of introduced plants providing food to native birds, etc. But what degree does introduced vegetation affect the balance of species eg crops that have enabled the corella and galah to proliferate and thereby compete for nest hollows, etc. On the other hand, native critters have lost a lot of habitat and in some cases introduced plants may help them to survive, particularly through lean times. Maybe I can use native bees as an example. I have often seen native blue-banded bees eschew flowering native plants in favour of Chinese plumbago, and the flowers of the basil (sweet, lemon and Thai) in my garden are very popular with tetragonula carbonaria, the native stingless bee. TC is supposed to have a range of only about 500m from their hive and the eucalypts in this area, although numerous, don't seem to be flowering at the moment. So I wonder what the bees would do without the basil.
The point of the article seems to be that in a disturbed environment, the behaviour of native animals is changed so much that simply replanting their original food source plants may not be enough to help the animals re-establish. In a broader land management context this is not so important because you are not just planting for the birds or butterflies. But if you have a narrower aim of attracting a particular group of animals, limiting your planting to indigenous species will probably be counter productive.
Thanks, Greg. Your explanation has clarified to some extent what you're arguing, particularly your point about agricultural practices reducing soil nutrients & the importance of rebuilding the level of nutrients in order to increase biodiversity (through plant establishment & wildlife attraction, presumably.) But even in this case I would have thought it important to allow farm fertilizers to leach from the soil before applying more natural fertilizer. In fact, one approach is to allow the farm fertilizers to leach from the soil then plant indigenous colonizers such as wattles to build up natural nutrients before planting a more complete range of indigenous vegetation.
I'm not altogether surprised that there was a higher level of invertebrate diversity in a pine plantation's litter than in nearby bush. All forms of life are opportunistic & will exploit whatever resources are available to them. However, the increase in invertebrate numbers in a pine forest's litter will almost certainly have an effect in some other area or areas of the ecology of that place. E.g., bird species X might travel from the native bush into the pine forest to exploit the increased supply of invertebrates thereby depriving plant species Y in the bush of pollination services profided by bird species X leading to a decline in the regeneration of plant species Y resulting in less resources for & a decline in numbers of marsupial species Z causing a proliferation of plant species Q.....Hopefully, this illustrates my point that if we're to achieve anything remotely approaching a natural biodiversity then as far as we possible we need to replicate what used to exist. The complexity of ecosytems, however, means that they're almost certainly impossible to replicate in their entirety. But it also demonstrates how when we need to know as much as possible about the ecology of an area before we mess with it or try to restore it.
As for studies comparing bird species diversity in indigenous & exotic revegetation projects I can cite the study I've made of bird species numbers on my 17 h.a. When we arrived 25 years ago there had been extensive revegetation with exotic grasses & some revegetation with native & non native exotic trees & shrubs, particularly the latter. There were 4 remnant indigenous trees a few remnant indigenous grasses & herbs. I counted 45 species of birds, 4 of which were exotic, in the first 6 months of our residence. Since then, having revegetated extensively with mainly indigenous species, I have counted 130 species. Perhaps this isn't a fair comparison because the structure & maturity of the two types of revegetation would need to be accounted for but the bulk of the exotic grasses would have been planted about 100 years before we arrived so in that respect the exotic revegetation was far more mature wehn we arrived than the indigenous vegetation is today.
Another example of revegetation with exotic speices is in Stirling in the Mt Lofty Ranges. In an albeit relatively small area (approx 2 h.a.) I counted over a period of about 4 hours 2 bird species, one native & one exotic. It could be argued that this isn't a fair comparison either due to the short observation time involved but in over 25 years of trips to Stirling where exotic vegetation dominates I can't recall, from casual observation, seeing more than four species, 3 native, one exotic.
Night Parrot, so often I think that these sorts of arguments are based on what people value most. However, I believe that the data I have obtained from my own indigenous revegetation efforts points towards planting with indigenous species producing greater diversity of bird life &, what is even more important, more natural diversity of bird life, than planting with exotics. I'd be surprised if similar results were not shown in other revegetation projects.
Chemicals, whether nitrates, phosphate or potassium etc are the same whether natural or synthetic. The big difference between natural and agricultural soils is the cycling of nutrients. In natural systems nutrients are trapped and cycled over and over again. In agricultural systems nutrients are lost through erosion, leaching and exporting agricultural product. There is no need to wait for nutrients to be washed away, let them be taken up into plant tissue and returned to the soil as litter. The other factor is organic matter. Nutrients allow more organic matter to be produced and build up in the soil, in turn the organic matter helps hold and cycle the nutrients. To wait for the organic matter to increase naturally is a very slow process. If you can add organic matter and nutrients you can accelerate the process considerably towards returning to the virgin soil fertility. On a large scale this can be expensive, and may be undesirable if it encourages weed growth. However on a small scale (suburban garden) it is a way to achieve something like the original soil condition, and encourage birds, butterflies ad other animals to visit your garden.
That makes a lot of sense, Greg, although I have a question mark on whether natural & synthetic nutrients are the same. Perhaps you have more expertise in this area than I'll ever have.
The point about the long wait for organic matter to build naturally is precisely why it's so important to preserve what we have left. It takes a few minutes for developers' bulldozers to wreck the bush but hundreds, if not thousands of years for it to return to its natural state - if it ever does.
You make a good point about the problem of nutrients encouraging weed growth. It's a disastrous practice used by many gardeners who live near bushland to dump their garden refuse, including lawn clippings, in the bush. Some do it to get rid of the rubbish, others do it because they think they're building up compost & nutrients to benefit the bush. In fact, they're providing ideal conditions for the invasion of weeds in addition to the weeds they'll introduce throught their garden refuse.
I'm pleased we've continued this debate for a considerable time because I feel I now have a much better understanding of where you're coming from on the question of nutrients so thanks for that, Greg.