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Thread: Increasing biodiversity?

  1. #1 Increasing biodiversity? 
    Forum Radioactive Isotope skeptic's Avatar
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    I am writing here as a New Zealander, and my knowledge of ecology is greater for NZ examples. My country has been lashed by the loss of species - 50 species of bird alone in the last millennium. The reason being the fact that our ecosystems evolved in the absence of mammalian predators for millions of years. Then came humans, and their 'passengers' like rats and other predators.

    We have lost two thirds of our rain forest habitats, and a lot of wetlands also. Due to people cutting down forest, and draining swamps.

    However, biodiversity has actually increased.

    Take the number of plant species. NZ has 2,000 native plants, of which about 6 have gone extinct. However, introductions of exotic plants have essentially doubled the plant biodiversity, with about 4,000 species of plant now thriving here.

    The same with animals. 50 bird species extinct, but at least 100 new species of bird introduced. If we are talking of biodiversity change, we have to say that human activity has, in fact, more than doubled the nation's biodiversity.

    The loss of native habitat has been replaced by other kinds of habitat. Rain forest is one third of its pre-human acreage, but there is now large areas of grasslands, pine forest, exotic scrublands and so on. A lot less wetland, but we now have large areas of lakes, with lake ecosystems, due to hydro-electric schemes.

    The question is whether the ecologies of New Zealand, (and other similar situations in other countries) have been impoverished or enriched. I have heard all my life about the importance of biodiversity, and the horror of species extinctions. But nothing is ever said of the other side of the coin. What of biodiversity increase due to species introductions?


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  3. #2  
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    What of biodiversity increase due to species introductions?
    Introductions or invasions?

    I think it's largely a matter of vulnerability, resilience and, above all, scale.

    NZ's problem with possums introduced into woodlands is much the same as Kangaroo Island's problem with the introduction of koalas. Neither were native. Both were introduced to islands to support a fur trade which disappeared just as the animal's population increased substantially. Culling is more of a management problem with koalas than NZ possums. Everyone thinks of them as 'native' animals even though they're not native to the island - and they're destroying the trees they rely on.

    But looking more widely. Perhaps NZ is fortunate in its latitude and its location. You don't have teak or rosewood tropical forests ready to be clear-felled. Nor can you establish large scale palm oil plantations if you cleared other forests. So you're not at the same risk as other places like Indonesia, Madagascar or New Guinea. And you're not big like the Amazon region to provoke anyone into large-scale (humongous scale) soy or cattle farming for the voracious meat market of the North American continent.

    Vulnerability. That's when we get to Australia. Vast expanses of nutrient and water deprived soils to start with. Add in rabbits, cats, foxes, camels, goats at the same time as scraping off the thin skin of scrubland and whoops! Sorry. Need to skin off the next delicate area, can't do anything here and the rabbits are eating our profits anyway. When you get to the wetter east coasts and the sub/tropics, you just let loose most of the first list and add in pigs, horses, buffalo and cane toads. When you find decentish crop growing land in the SW and SE corners of the continent, just use the worst cultivation methods you've ever heard of - mainly removing all those water table stabilising trees - and wipe out a couple of million hectares with salt accumulation. The area of farmland affected by salinity in Australia was about 10% of NZ's total land area 10 years ago. Haven't seen anything more recent.

    AFAIK Australia still holds the world record for extinction of mammals since white settlement. Always proud. And for diversity? I don't think the number of goats or camels raging through the denuded centre or pigs rooting through tropical rainforest has anything like the ecological value of all those small species of wallabies, bilbies and their ilk.

    The big issue really is whether the introductions and the associated land management have enriched or enhanced the diversity and relationships of the species in question or has the process simplified the ecosystems of the area. Simpler is less resilient, and therefore less desirable.


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  4. #3  
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    Adelady

    Do you know if Australia's total number of species today is more or less than before the coming of Europeans?
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    It's always worth bearing in mind that the word "biodiversity" itself is a controversial term that can be misleading and can be misused (unintentionally) to make unfair comparisons between one region and another.

    Typically it's used when describing the number of species in a particular habitat or location. A problem arises, however, in that some groups of organisms are very speciose - there are a lot of species in that group. Region "A" could have 798 species, for example, and region "B" 201 species. "A" is clearly more biodiverse, or is it? Region "A" may have 702 species of some insect that only a specialist with a microscope could distinguish. Region "B" may have a few species from each and every phylum, class, order and family (i know my numbers don't stack up). Is "B" more diverse than "A"? Or is "A" more diverse than "B"? Is diversity a measure of species numbers or a measure of evolutionary diversity?

    It's unclear what particular level one should use when discussing biodiversity: species? genera? families? orders? All of them? To muddy the waters, some groups of organisms have more members for no reason other than the mere fact that they have received more attention from biologists.

    Just random thoughts; I have no conclusion (yet).
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    Sorry skeptic I don't know. But I could hazard a guesstimate for various scenarios.

    Rivers, creeks and wetlands. Erk. Uncountable thousands of kilometres of river and creekbanks infested with willows which totally obliterate the aggregations of edge species. Broom and other weedy species take up where the willows leave off. Reeds and other water edge plants are only now beginning to be replanted into some areas where it's obvious to blind Freddy that the whole area is completely wrecked and overrun with weeds - after enthusiastic clearing and in some places 'beautification' of such areas. There are still lots of people who think that a river or creek is 'better' if every possible sq m of bank is 'greened' with neatly mown lawn grasses. I don't know any ecologists who might be able to tell me just how many plant and animal species are now MIA from such areas. But I'm not optimistic.

    Small birds. Certainly disappearing from suburban parks and gardens. Can't have prickly low-growing plants mixed up in shrubberies where delicate little kiddies might scratch a finger, can we. Where anyone thinks tiny birds which have always had to hide from bigger birds as well as other predators might find suitably protected nesting sites is beyond me. Everyone loves the little New England honey-eaters, but they'll skin their backyard bare and plant large succulents in neat rows of elegant pots around the swimming pool and think they're doing the world a favour - and wonder where the birds went.

    The only imported critters that have done us much good are the dung beetles. Dung beetles are the reason Australia was able to develop the street cafe culture. We used to have barbies and picnics for outdoor eating before but you really needed a third arm to wave off the flies. Once the dung beetles got to work and buried the cowpats, suddenly the outdoors is livable in the cities.

    This is depressing. I'll think about it a bit more and try some other searches for data - couldn't find anything much before.
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    Adelady

    Interesting you mention dung beetles. New Zealand is currently doing assessments of whether we should introduce them or not.

    Human generated environments are not necessarily bad. Australian Naturalist Tim Lowe, in his book , The New Nature, mentions the Melbourne sewage oxidation ponds as an example of wonderfully enriched nature, with a vast array of waterfowl species. He also says that town dumps (not land fills) are places where reptile life is enriched, due to the number of places, like under sheets of roofing iron, lizards and snakes can hide.

    As a scuba diver, my favorite example of human enriched environment is shipwrecks, where marine life is prolific. One theory is that the iron leaching from the wreck into the water is a nutrient that accelerates marine growth. Certainly they frequently have more species, and more density of life than natural reefs. In fact, I know of a rubbish dump off a particular island, where people for decades simply bulldozed their rubbish off a cliff into the sea, where the marine life is just amazing!

    However, my query was whether we could regard the increase in biodiversity from exotic species as an enrichment or an impoverishment. I suspect the answer might be unscientific and subjective.
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    Dung beetles are one of my super favourite thingies. There were some 'unscientific' types I saw a few years ago suggesting that native dung beetles would do the job. Well ..... no. They might, just, barely, cope with sheep pellets, but there's absolutely nothing among the native fauna producing anything remotely like a huge soft cowpat. Let alone a week's worth from a herd moving around a forty acre paddock. We need imports to bury the manure of the imports.

    Apparently, there are a few new species from the Mediterranean area of France having a nice little holiday in quarantine at CSIRO. The umpteenth generation of offspring are due for paddock releases a couple of years from now.

    Artificial reefs. A friend of mine wrote a book for the locals on shipwrecks off the SA coast a few years ago. I remembered we have several tyre, car body, deliberately scuttled dredge/barge reefs here as well as the wrecks. When I searched I found this. Fisheries | Do Artificial Reefs Work

    Looks like more research will have to come up with the goods if we are to get any more.
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    Interesting report on artificial reefs.
    I note, though, that their research was on shaped concrete reefs. If iron is the key, that is not going to work. Shipwrecks and dumped iron objects (cars, trucks, trams, boats etc) will show more marine growth.
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    The concern might be that in future millenia biodiversity is taken to mean that their are still Demcrats and Republicans.


    And nothing else.
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    Well, several of them are scuttled barges or dredges as well as one or two of car bodies. And the tyre modules are merely ballasted with concrete rather than turning into underwater concrete pyramids.

    I presume that the research would focus on the differences between the kinds of reefs as well as the aggregate picture of fish numbers and diversity as well as sea floor plant and other communities. I do like the idea of putting an artificial reef a mile or so away from a vulnerable shipwreck, though, regardless of the biodiversity/fish number issues. It means that the wreck can survive longer as a diving and scientific site, while more casual fishing promoted by the concentration of fish can happen away from the wreck itself.

    Country reefs fishSA.com - Artificial Reef Locations [Hot Spots - GPS Locations - Country] Metropolitan beaches fishSA.com - Artificial Reef Locations [Hot Spots - GPS Locations - Metropolitan]
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  12. #11  
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    Have to figure that human interference is creating new environments and niches that never existed before. If the environment never changed, evolution would slow down to a crawl, because each species would adapt to optimally fill its niche and then stay there (can't really improve on perfection.)

    If new niches are emerging, the probably species are going to start changing to adapt to them. I know raccoons exhibit some interesting behaviors when they find themselves near a human settlement. They seem to have adapted very well.
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    If new niches are emerging, the probably species are going to start changing to adapt to them. I know raccoons exhibit some interesting behaviors when they find themselves near a human settlement. They seem to have adapted very well.
    I know all this. I think I'm a bit over-sensitised having moved house less than a year ago. I reckon in the previous 35 years I would have seen no more than a couple of dozen snails. My old house in an old suburb on a large block had more than 4 families of blue tongue lizards living under various fence, tank, shed structures as well as stacks of spare tiles, timber and bricks. (I made sure some stayed in place - out of sight, out of walkways.) They dealt with the snail population quite happily without bothering us.

    Down here I know there are no lizards controlling the wretched things. Our garden is infested with the useless parasites. There are lots, heaps in fact, of large open parks separating parts of these southern suburbs. But they're all neatly mowed grasses with stands of medium to large trees. No accumulations of logs or litter for small reptiles to maintain a home base. Very little in the way of prickly/tangled/smallish scrub or undergrowth for vulnerable little things to stay safe in. We have lots of magpies and galahs and rainbow lorikeets (no kookaburras though) but no small birds of any kind, I've not even seen sparrows yet. Haven't seen any little geckos either, come to think of it. That might be just a seasonal or weather thing, it's been very cool and damp these last 12 months. I doubt we've had too many weeks, certainly not a month, with no rainfall.
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    WYSIWYG Moderator marnixR's Avatar
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    Quote Originally Posted by skeptic View Post
    However, biodiversity has actually increased.

    Take the number of plant species. NZ has 2,000 native plants, of which about 6 have gone extinct. However, introductions of exotic plants have essentially doubled the plant biodiversity, with about 4,000 species of plant now thriving here.

    The same with animals. 50 bird species extinct, but at least 100 new species of bird introduced. If we are talking of biodiversity change, we have to say that human activity has, in fact, more than doubled the nation's biodiversity.
    but how about global diversity ? at a local you've more than replaced species gone extinct, but what went extinct didn't exist elsewhere, whereas the replacement are common elsewhere - hence globally the species count has gone down
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    hence globally the species count has gone down
    There are infrequent - and rather amusing - exceptions or contra examples.

    Adelaide's dry environment - more Mediterranean than the Mediterranean as some people say - is absolutely ideal for olive trees. Several orchards were planted very early during settlement. And they went wild. Damn things absolutely everywhere, especially in the Hills.

    So a couple of decades ago people started ripping them out in a big way. Until the real Mediterraneans pointed out that this was the only source in the world of diversity in the genome from cross breeding in the wild. Greece, Spain, France had all focused their growing on very few species for cultivation and there were no other sources of new genetic material for further or improved breeding.

    Similar issue with camels. The Afghans brought camels over for desert transport a very long time ago. They also went feral in the congenial conditions of Central Australia. They are a dreadful pest and a blight on the ecology/landscape. When someone suggested to a couple of Middle Eastern countries that we might kill them and send the meat as a way of making money while culling - they got a bit of a surprise. Turns out Middle East people have been focusing on a few strains of camel for particular purposes and they were short of wild genetic sources to improve their breeding.
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    Quote Originally Posted by marnixR View Post
    what went extinct didn't exist elsewhere,
    I have this feeling that, in terms of ecosystems, the species that go extinct don't actually make a lot of difference.

    Of course any extinction is a tragedy. But does it alter the ecology? The species that are vulnerable to extinction are usually in restricted numbers in the decades before extinction, and the local ecosystem will already have altered in response to the fact that the vulnerable species has largely disappeared. So the final extinction has little or no impact on the ecology.

    The species that have the biggest impact on ecology, for good or bad, will be the most abundant species, and hence the ones least likely to face extinction.

    The world has a measured extinction rate (where organisms that have been described scientifically are later found to be gone) of 10 to 20 species per year. There may be a lot of other species never described that go extinct, but these too will be small in number. Is a rational conclusion that these extinctions actually make little difference to global ecosystems?
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    Of course any extinction is a tragedy. But does it alter the ecology? The species that are vulnerable to extinction are usually in restricted numbers in the decades before extinction, and the local ecosystem will already have altered in response to the fact that the vulnerable species has largely disappeared.
    I reckon there might be a hint of case-by-case here. I had thought of all those little forest and woodland marsupials that have largely disappeared (due largely to foxes, cats, rabbits on top of habitat loss) as being extremely cute and desirable in their own right. I'd never thought of them in terms of "ecosystem services" to use the standard wording. It turns out these little scattered creatures had a role in maintenance and regeneration of their ecosystems. (I did know that they were useful in keeping the forest floor clear of fire encouraging debris.)

    They have small appetites and consequently small pellets of manure - which they deposit by scratching the surface of the soil. Apparently these little depressions are enough to gather a bit of leaf litter, concentrate and hold moisture and generally provide the ideal seedbed for any seeds which can't help but roll into the depression. The combination of protection, leaf mould, fertiliser and moisture is enough to give trees and shrubs a good start in life.

    None of the animals and plants which have displaced these creatures do anything at all to maintain those environments. None.
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    Quote Originally Posted by adelady View Post
    There are infrequent - and rather amusing - exceptions or contra examples.
    it strikes me as rather ironic if an introduced species was considered a pest when in its home territory it's thought of as endangered or genetically impoverished
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    Of course any extinction is a tragedy. But does it alter the ecology? The species that are vulnerable to extinction are usually in restricted numbers in the decades before extinction, and the local ecosystem will already have altered in response to the fact that the vulnerable species has largely disappeared. So the final extinction has little or no impact on the ecology.

    The species that have the biggest impact on ecology, for good or bad, will be the most abundant species, and hence the ones least likely to face extinction.
    The species with the biggest impacts on the ecology of the NA eastern woodlands in the year 1492 included humans (replaced by another variety with completely different ecological roles), woods buffalo ( dominant grazer and browser), American Elm and American Chestnut trees (lowland and upland dominant vegetation, respectively), grey wolves and cougars (dominant predators), passenger pigeon (by far the most common bird), sturgeon and salmon and oyster and menhaden (various aquatic), and so forth.

    They're all gone now, from large regions which they once dominated - effectively extinct, at least in reference to their former roles. Naturally most extinctions in NA were of lesser and less visibly influential species, but then most species are lesser and less visibly influential.

    The ecosystems remaining after the elimination of these species have been radically and fundamentally changed. The fact that these changes took place over a few decades of decline, usually, rather than all at once when the last one died or whatever, is irrelevant.

    Biodiversity has a variety of measures - the simplest reasonable one is probably Pielou's , but it has its critics All of them are meaningless without a defined region or landscape or taxonomic category or some such boundary.
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