Dynamic ecology as described by Vera means an alternative approach to conservation (1 Viewer)

[Shadow-watcher]

I recently spent alot of money on a book entitled 'Grazing Ecology and Forest History' by Franz Vera as part of my research into ecology. The book is a extensive explaination of the thesis that Vera produced as part of his work in the Dutch ministry of agriculture and conservation.

The thesis was produced in 1998 and provides an alternative hypothesis to the conventional belief that Europe's ancient ecology was comprised of a closed canopy continuous forest. Vera argues that this is incorrect, and that the traditional theory of climatic succession, culminating in a closed canopy forest is ignorant of the impact and ecological effect of large herbivores on the landscape.

With these effects added the result is an ecology which resembles a parkland. Fragmented forests existing amongst swards of grassland, in which thorny shrub species eventually establish, providing grazery protection for saplings which develope into small forests. These woodlands then, over many years, establish before dying of old age, providing glades allowing grazers to open up the forest back to grassland.

Much of modern conservation is concerned with maintaining high biodiversity and conserving species, in respect of the climax model of a fixed closed forest being the ideal. But Vera's study highlights the great shifts in ecology over a greater and more realistic timescale. This moves the focus of conservation back (in my opinion) to a more preservational approach, but where the emphasis is now on the preservation of long term dynamic ecologies rather than a stable climax ecosystem.

Understanding the scale and degree of ecological change, in terms of grazery (now provided via agriculture) and habitat as grassland and forest is massively important for birds, and may help us understand why some of their numbers continue to decline.

The traditional framework of conservation, which is still very prevalent in modern conservation organisations, will shift to a different approach toward the protection of shifting ecologies, rather than high biodiversity. Or at least it must if we truly strive for healthy natural systems.

And that puts a very different spin on things!

Regards

 

[Reuven_M]

I can't see much here I disagree with at all. I have thought several times that the unbroken forest present at the arrival of Europeans in North America must have been much less continuous when there were mammoths, giant camels, giant ground sloths and other massive herbivores wandering around.
An awful lot of people seem to feel that any species decreasing in numbers is a conservation issue, while ignoring that many other species may be increasing.

 

[King Edward]

Much of modern conservation is concerned with maintaining high biodiversity and conserving species, in respect of the climax model of a fixed closed forest being the ideal.

This is simply not true. In fact, I would argue the reverse. Modern conservation literature (in the UK) is full of the benefits of 'conservation grazing' and the importance of managing 'semi-natural' habitats such as meadows and heathlands. There is very little emphasis on the importance of closed forests, especially old growth forest communities which are essentially absent from the country.

The main problem with Vera's model of a parkland-type landscape is that it just isn't true. It sounds attractive, but the evidence is against it. In the absence of humans, the UK would be very largely forest and wetland. Where large herbivores (and fire) can have an impact is in savanna-type environments where limited water availability makes conditions marginal for tree growth, so that fire + grazing can shift the balance towards grassland. This is clearly not the case in Britain where the temperature, soils and climate are highly suitable for forest development, with the exception of the higher uplands and very wet areas.

Vera also completely ignores the effects of large predators on herbivore ecology.

In answer to Reuven, North America was not continuous forest but has long had large areas of grassland especially in the dry continental interior. The natural vegetation type of an area is generally determined by the climate and other abiotic factors - forests naturally grow where the conditions are suitable, and don't grow where they aren't.

The Mammoths were more creatures of steppe-tundra, the disappearance of which is due to the warmer, wetter interglacial climate and not due to lack of Mammoths.

I am all in favour of conservation emphasising natural communities and ecological processes, rather than continual management to recreate the specific habitats associated with olde-worlde farming practices, but that needs to based on genuine ecology and not some fantasy such as Vera's.

 

[Reuven_M]

In answer to Reuven, North America was not continuous forest but has long had large areas of grassland especially in the dry continental interior. The natural vegetation type of an area is generally determined by the climate and other abiotic factors - forests naturally grow where the conditions are suitable, and don't grow where they aren't.

Of course there was grassland, I just meant the deciduous forest of the East. This area was essentially unbroken forest over much of the East.

The Mammoths were more creatures of steppe-tundra, the disappearance of which is due to the warmer, wetter interglacial climate and not due to lack of Mammoths.

I did know this, not sure why I added mammoths, but the point is that there were far more big herbivores around.

I am all in favour of conservation emphasising natural communities and ecological processes, rather than continual management to recreate the specific habitats associated with olde-worlde farming practices, but that needs to based on genuine ecology and not some fantasy such as Vera's.[/QUOTE]

 

[lashinala]

I absolutely agree that the forests were more broken up. Heck, after all the tornadoes we see on a yearly basis, weather alone will keep too many areas from being a constant tree canopy around here. add fires, straight line wind blasts, etc. and there were plenty of areas free of canopy.

 

[Shadow-watcher]

This is simply not true. In fact, I would argue the reverse. Modern conservation literature (in the UK) is full of the benefits of 'conservation grazing' and the importance of managing 'semi-natural' habitats such as meadows and heathlands.

OK happy to concede that there is a great deal of grazery conservation, I work in it, but the closed canopy forest is considered the climax of ecology through succession, and has great influence in how we view forest conservation to be specific.

As for the main problem with Vera's hypothesis being that its simply untrue, I would argue the main problem with vera's hypothesis is pollen diagrams. Specifically those created in relation to pollen samples taken by Mitchell from peat bogs and lake sediments across lowland Europe. These results reject Vera's theory initially, but may actually prove it considering the pollen samples include species which only exist in open forest/grassland systems.

Also palaeoecological studies like this one...

http://www.knepp.co.uk/Other_docs/Frans%20Vera/Whitehouse_and%20_smith.pdf

...are further showing the ancient forest to be a far less dense and more patchy arrangment than previouisly thought. :t:

forests naturally grow where the conditions are suitable, and don't grow where they aren't.

And also there are very few areas where a tree wont grow if free from herbivory, hence they have established in one form or another in almost every environment on earth.

 

[Mysticete]

Mammoths were by far not limited to arctic steppe, and only the Woolly Mammoth was especially adapted to this ecosystem. North America had between 3-4 additional elephant species, including the Columbian Mammoth, which was found throughout the southern tier of the North America, and was probably adapted to open savannah environments.

Many of the ecosystems present during the last glacial don't exist today, and are referred to as Non-analog communities. For instance, in the east you could find Eastern Chipmunks, Plains Pocket Gophers, and Lemmings all hanging out in the same area. Similar associations have been recorded among flora, and at least some of these ecosystems seem to have been a result of landscape alteration by megafauna (such as Spruce Parkland).

 

[King Edward]

One of the main difficulties in determining 'natural' vegetation is the changes in climate that have occurring since the last ice age (and continue to occur). In a situation where large areas are changing from a glacial/post-glacial environment to a more temperate one, with simultaneous colonisation by trees, other plants and animals etc. (and humans) it becomes very complicated. In such a situation, especially considering that much of the landscape would likely be pretty wet, a whole mix of habitats is indeed quite likely. Where areas are marginal for tree growth, for instance because of low temperatures, waterlogging, nutrient impoverishment or whatever, it's quite plausible that large herbivores could play an important role.

That's quite different, though, to Vera's landscape cycling hypothesis in which forests are unable to regenerate due to herbivory and continually collapse and regrow elsewhere. The question is not so much whether open habitats existed, especially relatively early in the post-glacial period, but whether they alternated with forest cyclically.

 

[Mysticete]

There are plenty of incidences of shifts in forest structure due to to herbivory. In the US (and Europe?) overgrazing by herbivores in the absence of predators has resulted in some species having 0 recruitment in certain areas, causing a shift towards different plant species. And it's well documented that parks in Africa that have had all the elephants poached out often shift from more open wooded savannah to thick brush. Large herbivores might also play other roles as well, including accelerating of nutrient cycles (or transfer of nutrients via dung).

 

[King Edward]

There are plenty of incidences of shifts in forest structure due to to herbivory. In the US (and Europe?) overgrazing by herbivores in the absence of predators has resulted in some species having 0 recruitment in certain areas, causing a shift towards different plant species.

Yes, in the absence of predators. I think that's one of the main problems with Vera's hypothesis - he doesn't properly consider the effects of predation on herbivores. As far as I know his ideas are based on the Oostvaardersplassen in the Netherlands, which has several species of free-ranging large herbivores which keep the vegetation open but no predators. For example, in 'Large-scale nature development – the Oostvaardersplassen' the only mention of predation refers to Lions in the Serengeti, an example of dubious relevance which he uses to dismiss the relevance of predators to herbivore population control.

And it's well documented that parks in Africa that have had all the elephants poached out often shift from more open wooded savannah to thick brush.

This is the sort or transitional grassland/woodland environment where herbivores (or small changes in e.g. rainfall) can tip the balance towards a more open environment. I don't think it's that relevant to the UK situation where conditions are generally much more suitable for tree growth.

Edit: I meant to add earlier, my main practical concern about Vera's hypothesis is that it downplays the importance of old growth climax forest as a valuable habitat, and can be used to justify a more interventionist approach to conservation-oriented forest management aimed at encouraging open habitats. Not that the latter are undesirable, far from it, but there needs to be more focus on the high quality closed forest than at present (in the UK at least, I don't know about the situation in the USA).

 

[jurek]

This is a big topic, which was long discussed on some forums, so just quick:

- In Europe, there was research on paleoenvironment during the last interglacial ( ca 110,000 y ago, when climate was similar to today). Lots of plants and animals associated with open country existed, as well as forest species.
- So definitely there was lots of open habitats. If they were kept open by herbivores it is not known. If they followed Vera's cyclical approach is not known either.
- Historically, floods, forest fires and suchlike didn't produce large open habitats in Europe, so perhaps herbivores produced them by elimination.
- Vera doesn't convincingly discuss role of predators, nor whether todays cows and horses could replace straight-tusked elephants and suchlike.
- Oostvaarderplassen and similar such reserves in Holland are interesting, but AFAIK many open country species don't occur in them. So it is unsure if they restore really natural ecosystem (besides openness of habitat).
- Conservationists in Poland argue, that wolves and lynxes are able to keep population of herbivores in check, and some plants can regenerate in closed forests, unlike what Vera said.
- Proving Vera's ideas would need enormous areas and timescale of decades or centuries.
- Veras idea of "protecting ecological processes" is very vague in practice. We must conserve species, because if they die out, they cannot be ressurected to life. But ecological processes - are poorly defined, their existence is poorly proven, they are difficult to observe in a normal time-scale, and may be used as an excuse not to conserve species.
- Old-growth forests are now very rare in Europe (especially ones with decaying wood) and are much less common than both traditional and Vera's model predict them to be.
- Large herbivores (especially European bison) and carnivores are rare in Europe, and it is not sure if Vera's ideas help their reintroduction or not.

- In North America, there is little such research, besides glacial (Ice Age) plant communities, which are of rather little relevance to todays climate. So there is no baseline data what ecosystems "should" be.

So a bit confusing picture, whether yes or not.

I would prefer protecting species, and think about herbivores only when they are rare (European bison!) or really help other rare species.

 

[Shadow-watcher]

Just to say this is the kind of discussion I'd hoped would take place, and thank you all for your valuable input.

From my understanding;

Vera isnt interesting because he advocates a cyclical forest model. All forest ecologist attest to one form of cycle or another, but generally all those various cyles are slightly different views of Watt's gap model, where by some disturbance ie, tree death or windfall are the meachanism by which forests are opened and regeneration takes place.
The swiss forest ecologist Leibundgut (1959) was the first to describe the way prmeval mountain forest went through a number of stages in terms of structure. But earlier Watt had distinguished it was a 'gap phase' which allowed for the cycle to start over. Watt's gap phase model is a paradigm of forest ecology and as such is considered for all intense in purposes a 'truth'. Vera's work is interestesing because of the role he places on herbivores within these cylical processes.

Importantly all the cyclical models are not unilateral to a whole forest, but revolving throughout a forest at different stages and at different rates. The 'shifting mosaic steady state model' is interesting if you fancy researching.

What all the other models have in common is that they superimpose factors on the gap phase model from outside of the system. Within these models herbivores follow the developments within vegetation, and are responsible for a retrogressive succession from forest to grassland. Vera says this is wrong, and that in the lowlands of europe the vegetation resembled a park-land like landscape where by large wild herbivores and facilitator species like the Jay determine the species of tree that develope, ie the vegetation follows the herbivores.

The time frame of relevance is that from the most recent late glacial period, ending in europe some 13-14000 BP, and its this time frame we reference when we consider conservation ideals (for lowland forests).

This is a big subject and we cannot hope to cover it here, but its an interesting one none the less.

Lastly does anyone know some other good forums for this kind of topic?

 

[Tideliner]

There can be little doubt that following the last ice age our natural forests have waxed and waned to some extent with climatic and biological effects ( defoliating insects disease \ fire \ flood \ severe winters may have had a big impact allowing mammal herbivores to gain a short lived upper hand over the forest on a limited basis.

However we also need to question just how large were the forest herbivore populations. In the case of insects they may well have been substantial , but for mammals they may well have been comparatively small. In tropical rain forests large mammal herbivores are quite scarce compared to the open grasslands. Trees present a physical barrier to many large mammals. My own opinion was that our ancient forests were quite stable at their heart , but along their fringes herbivores could and probably did have some short term impact , perhaps more important in dry climatic periods , but less so in wet periods.

In a UK context we cannot afford the luxury of widespread forest \ grassland ecosystems with their large herbivore \ predator populations. The majority of our woodlands and fragmented ecosystems with insufficient space to allow Vere’s hypothesis to take place. We have to halt the succession of our woodlands \ grasslands at a fixed stage as they are too small to allow many species to move with the ebb and flow of succession

 

[LabradorDuck]

I don't know too much about the habitats in Northern Europe, but in North America at least some ecologists feel that open forest/savanna-type habitats were more widespread that has been previously recognized. To me it seems that there was almost certainly some shifting between habitat types, with the exact vegetation depending on long-term weather trends and how long a particular area had been without fire or flood. Large herbivores were probably a factor as well, but it's hard to say how much of an effect they would have had on their own.

From a conservation perspective, it's best to let natural processes occur as much as possible, but on small preserves there just isn't the room. If, for instance, a large patch of woods burns down, there probably isn't another patch nearby from which species can re-colonize. Maybe we need to preserve more "early-" and "mid-successional" habitats, but within small preserves at least some intervention will be necessary.

The other thing about open forests is that, with some notable exceptions (Red-Cockaded Woodpecker springs to mind) many of the species that would have been common in such habitats are probably the same species that do well in suburban/rural habitats.