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Subject: [Hong Kong] Time to chop down paper bark trees? 應否斫掉大埔滘的白千層？ [Print This Page]
Author: wmartin    Time: 9/09/2008 12:21     Subject: Time to chop down paper bark trees? 應否斫掉大埔滘的白千層？

For some time now, I've believed it would be good idea to chop down many/most paper bark trees in Tai Po Kau Forest reserve.

Walking thro paper bark groves, they seem pretty bad for birds - and, by the looks of things, biodiversity overall. Not much else growing there; in an otherwise diverse forest area, seems a bit like monoculture - akin to gigantic wheat field!
These trees are often big; but felling them might help some of existing other trees grow, as well as more saplings etc, leading to enhanced biodiversity here I reckon. (Yes, something of a guess on my part - I'd be intarested in opinions here)

Prompted to post this morning as only just come across this:

December 2001, Porcupine! 24: 19-20
Is Paper Bark Tree becoming invasive in Hong Kong?
By Billy C.H. Hau
[not quite same issue - the paper barks in TPK were planted, I believe]

Even if naturalists in HK were to support idea, perhaps removing a few trees as a test, I imagine more than a few desk bound bureaucrats might be startled by the notion.

[ Last edited by Webcreeper at 12/09/2008 04:18 ]
Author: HFCheung    Time: 9/09/2008 15:03

Support.  This suggestion is not new.  It should have been done long time ago, but, in line with civil servent tradition, "no work, therefore no fault".  It would take more time to replace those trees.

HF Cheung

[ Last edited by HFCheung at 10/09/2008 20:37 ]
Author: wmartin    Time: 10/09/2008 09:52     Subject: down with paper barks!

I hadn't heard re this before; but not at all surprised re officials. [As pretty much common knowledge in oonservation, really protecting biodiveristy doesn't just mean hands off approach, esp when it comes to exotic species.]

I emailed Billy Hau (assistant prof in HKU's ecol n biodiv dept] re this; his response:
Quote:
I would say in fire prone area, they should be cut because fire will allow the species to spread. If there is no fire, they will not be able to reproduce as their seeds will be trapped in the seed capsule and cannot germinate. This species needs fire to reproduce even in it's native range i.e. Australia. Those in TPK is probably ok. The strategy may be to thin out some of them mature trees and at the same time plant some native tree seedlings behind them. This improvement process will take a long time but we need some patients to due with forest.
As well as Tai Po Kau, there's also major paper bark stand in northwest Shing Mun area - roughly west of the real nice fung shui wood. Another place where I find birding quietens down a lot.

I also sent email re paper bark chopping to KM Yeung at AFCD; rather hope he'll pass to someone who will reply. But - as w H5N1 (and Deep Bay's rising mudflats) - science based replies not always the forte of afcd; hope this proves different.

[ Last edited by wmartin at 10/09/2008 09:54 ]
Author: lmichael    Time: 10/09/2008 10:20

I have long considered that some at least of these should be felled. There is now an ample seed source for native species so it would not even be necessary to plant (though that would speed things up and probably result in better diversity (otherwise the bulbuls will probably largely spread Machilus).

In addition to the Melaleucas I would suggest removing the Tristania - these also support a very impoverished bird community.

It may also be a good idea to ring bark but not fell some - we need more dead wood in TPK which is typical of young forests with few dead or senescent trees which are valuable for woodpeckers and barbets (and lots of other birds once they have made holes in them.

Mike Leven
Author: lwingkay    Time: 10/09/2008 13:02

Interesting to read the emails in this thread, especially Wmartin's quote from Bill Hau's reply.

I am more layman than many a layman in Hong Kong about forestry. Dr Hau’s did make more a bit more informed about the paper bark trees. I do hike, too, sometimes. These are the background for the following points I would like to make in response to what Wmartin had initiated here:

a) It seems to me that the distribution of the paper bark tree in Hong Kong is pretty confined to the roadside, the reservoirs and their catchment areas. Probably, they have been planted there in consideration of their ability to adapt to extreme dryness and severe water-logged situations, which are exactly the case for the roadside and the reservoir areas. It seems that the distribution is not to a rampant stage, posing threat to fire safety and biodiversity.

b) I have no ideas whether birds dislike frequenting the paper bark or not. Probably, the seed capsule is too hard for birds to open and the smell of the crushed leaves is offensive, so the latter prefer other trees. However, I do see insects and birds loitering by the brush-like flowers from time to time and perching on the branches to rest or among the foliage to hide. The paper bark may not be like, for example, the mulberry where birds like visiting but it definitely is good to the bird in some respects.

c) Even if the paper bark is not preferred by the birds and its bark too brownish grey to be aesthetically attractive, it is not reasons enough to have them chopped for there are still other functions that they can discharge in their habitat, e.g. providing a windshield for other plants, greening our environment and holding up top soil from erosion. Chopping is favored when their aggregation in a certain place is to a level that poses fire risk and negative effect of biodiversity.


d) The prolifieration of paper bark trees in TPK and Shing Mun Reservoir is more than natural, a place where there is plentiful supply of water. Probably, they are one of the best species to cope with the environment and there are few species that can proliferate under their crowns now. In fact, due to the fact that the seed capsules are difficult to break, as Dr Hau says in his reply, in the absence of high temperature, there is a slight chance that the paper bark can further extend their reach to the locality beyond their own groves. So, as regards the whole landscape in the forest, macroscopic biodiversity is still in place. The paper bark grove is only a concentrated presentation of the paper bark species in the whole natural environment of the locality, posing no threat to the overall biodiversity.


About the issue of bureaucracy mentioned in the emails, would like to say a bit about my view. Frankly speaking, chopping or not chopping is an issue that concerns few people. Most of us concern about the presence of more trees around us as measures to keep the air fresher. However, when it comes to a decision, the issue usually become politicized and most of the time, it ends up in a political farce. And because of this, the government has to take every precaution to balance the interest of different parties in our society; otherwise, the government will be in deep shit. So, I tend not to say that the government is slow with everything. They simply have lots of things to take into consideration. Perhaps, there are members in the civil service who are reluctant to do what they should to have their work done properly but most of them are obedient and industrious, who really want to serve well. What lying in the road is the interest of the public that they have to balance, which has made it difficult for work to be discharged at a rate that we laymen expect it to be like. It is therefore judging to say that they are insensitive to public opinions, desk-bound or that they do less to avoid committing mistakes. We, onlookers, set out from our own perspective and look out differently from our own dens but the government has to be encompassing in the course of administering for the wide public. No matter what, it is worth the while to put ourselves in others’ shoes sometimes.

'Chopping or not chopping' is a healthy issue worthy of exploring into for the sake of the long-term health of our forest.  It seems that from time to time, our government has the need to do something about its forestation policy to make it well conceived of and long-term in context as far as practicable. The planting of Acacia confusa is a lesson that the government can learn from as this exotic species from Taiwan grew so rampantly in Hong Kong that it eventually becomes invasive to the local species, posing threat to biodiversity and change to the local forest landscape. They should consult naturalists and botanists for timely policy change from time to time.

Have to say that I am like the majority. I want to have more green trees and I seldom bother what species they are. Wmartin's reminder here does give me something to think on and to learn from regarding loving our natural environment.

Peter
Author: HFCheung    Time: 10/09/2008 20:57

I have heard about the issue about 5 years ago.  I can imagine AFCD know this issue/proposal much earlier than I did.  I really like to see wide-spread/deep consultation discussing the issue, or some assessment/feasibility study in this area.  I beleive most of the public have not heard about this and probably found it odd if the government is to take the lead to kill some very big healthy trees.  Tree planting is very popular and highly supported by the public, but, from time to time, I heard people talking about there isn't sufficient thought on selecting the proper trees to plant.  So HK continue to plant trees that may look good, but have not realised the greatest benefit to the whole eco-system.

Most the previous suggestions are really good, and have been discussed before.  Somehow, no action has been done.  I hope we can make sufficient noise this time, and make AFCD think about it more seriously.  My guess is that it will drag on.

I understand balancing the public interest, but I doubt whether the public has been properly involved at all.

HF Cheung
Author: ajohn    Time: 12/09/2008 14:09

I agree that it would be useful to thin out some of these paper bark trees. Although the area in TPK with these trees is sometimes used by birds, the overall numbers and diversity seems to be relatively low (mostly Velvet-fronted Nuthatch and Chestnut Bulbul). I suspect the same would be true for other species groups (insects, plants, etc.) This is probably largely because the understorey vegetation and ground cover is poor compared to other parts of the forest. I do not think large-scale felling is the solution, but agree with the suggestions that a ew trees should be targetted for felling or bark-ringing. This should open gaps in the canopy allowing other species to colonise, as well as creating dead wood; much like the conditions in natural forest.

Presumably these trees were planted for a purpose - as a fire-break or to increase tree cover? Now that the forest has regenerated in the area I think they have served this purpose and should be replaced by native species. This will take a very long time if we wait for natural death of the trees.

The other area at TPK that seems to require similar action is the area at the end of the red/blue walks, near the forest road; this area rarely contains birds and similarly has impoverished undergrowth vegetation. I think the trees may be the Tristania mentioned in Mike's earlier post. The same is true for plantations in other parts of Hong Kong (Shing Mun, Kap Lung, etc.)

I understand Peter's point that government needs to consider various options before taking any action, especially in the Country Parks or Special Areas.  Presumably they would need particular authorisation to undertake any management of this type.  Most of the public would not accept AFCD simply going into the forest to cut down trees, but would not necessarily object to small-scale removal of non-native species for an overall benefit to biodiversity (which is what is being suggested here). Public consultation and explanation would be necessary. AFCD should, however, be taking responsibility for management of the Country Parks to benefit biodiversity - if this is best done by removing non-native trees, then that is an option they should be seriously considering.
Author: wmartin    Time: 13/09/2008 10:49     Subject: down with paper barks and up with biodiversity

Glad this has prompted some discussion, and there is some similar thinking from folk who know re birds etc.

As I understand it, paper barks planted in several places as they can grow in damp areas (even places that are flooded at times).
But, to me, they're too extensive already; I'd be up for retaining, say, the paper barks that grow right by Shing Mun Reservoir, and have bases underwater when the reservoir is very high. But those in northwest of the area are on what could be prime site.

Wider biodiversity is impacted.
Tai Po Kau, say, is tiny by forest standards; and within this, the area of good tree diversity is tinier still (if other tree species could use some thinning, to give more diversity a chance, would seem good too). Plus, typical to get biodiversity higher in lower areas, and closer to streams - so paper barks here, and at Shing Mun, "hogging" what should be one of richer parts of the forest. With better trees here, will get wider benefits.
Hong Kong has close to 400 native tree species; not at all a place where it's remotely natural to have single species stands dominating sectors of prime areas. In moist tropics, a tendency for tree species to be well spread, so an individual here, another there. This in turn leads to greater diversity overall; and surely more attractive to human visitors, even if they don't care too much about finding certain birds, butterflies or whatever.

Intersting re having them killed and left to stand, rot. Some, anyway.

Should be possible to find expert advice on such matters, inc from overseas.
I reckon Hong Kong should serve as strong example of forest regeneration in the tropics. (Reached this conclusion partly after reading some research on forests and conservation in Borneo: plenty of info there on forests that had been felled to varying extents, but not on planted/regenerated forests that were some decades old.)
But this example is based on far-sightedness in the past: what a superb idea to make Tai Po Kau a special area, with species diversity!
Nowadays, some more far-sightedness - and even courage(!) - could be helpful.

Already, Hong Kong's forests are immensely impoverished compared to their original state: can only guess what we have lost. (No breeding woodpeckers shows the terrible effecitiveness of past deforestation: should be several species here, based on sub-tropical forest in region)
Holding back biodiversity not so good, now, unless for strong reason.
Author: lwingkay    Time: 14/09/2008 11:04

Did pay more attention to the natural landscape around us lately as a result of the discussion initiated here. Tended more and more to agree to felling some trees in some specifically chosen spots in order to enable more varieties of species there to thrive and to add value to those spots by nature of functions that they have been serving among Hong Kong people.

Did surf the Internet about the paper bark trees issues and most of the pieces I read were for the argument that the quantity of paper bark tree in quite some countries has been to an invasive level affecting indigenous species. Frankly, this surprised me for I did not know about that before; I have been thinking many a Hong Kong people do not as well. Here is a pick from the Internet that systematically outlines the reasons behind the invasiveness: http://www.nps.gov/plants/alien/fact/mequ1.htm.

Understandably, opinions/feeling about 'chopping' must be pretty mixed if they are to be fielded for wide consultation, especially in recent years when more and more people are concerned about protecting trees and idyillic plant groves in our natural landscape. Evidently, empirical data is essential for putting up a strong case that chopping is good for the environment and biodiversity, and that it will do no harm whatsoever to the species-specific groves.

It seems, however, that at present, most of what we have about the advantages and disadvantages of the paper park tree are common-sensical in content or textbook-based prediction/deduction which may be out-of-context with the situation that we are having in Hong Kong, e.g. TPK as mentioned here.

Further, whether or not bird biodiversity is really associated with the dominance of paper bark trees in TPK is still probably something pending to be verified. Perhaps, there are more effective means to do other than chopping.

In the meantime, the public has to be informed of the pros and cons so that they are able to make informed judgment of their own.

Obviously, AFCD and parties interested in this issue have to carry out investigation to justify their course of action.

Admittedly, for many a member like me who used to concerns predominantly about greenness and who is ignorant of the subtlety in ecological balance among species, this thread's sharing is a good chance to expands my horizon about biodiversity. Thanks.   

Regards,
Peter

[ Last edited by lwingkay at 14/09/2008 11:09 ]
Author: lwingkay    Time: 15/09/2008 08:39

Here is the link to Dr Billy Hau's paper on paper bark trees in Hong Kong in Porcupine, Issue 24 of December 2001.
http://www.hku.hk/ecology/staffh ... Kong-Hau%202001.pdf
Peter
Author: cgeoff    Time: 15/09/2008 12:51

My experience with AFCD is that there is a horror within the dept at the very idea of chopping down trees, even if they are exotic, planted species that could be replaced (as part of a development proposal, for example) with native species that would, ultimately, enhance local biodiversity. I would fully support selective felling of most of the paper bark trees and allowing natural succession to take over. The area at TPK where they are concentrated is, in my experience, very uninteresting in terms of birds. I think I may have written to AFCD many years ago suggesting the removal of these trees, but can't remember now.

The chopping down of trees is a management tool that I believe could also be used much more at Mai Po NR, where I believe extensive areas of trees are out of place. What we need there is large open areas of freshwater marsh, not brackish lagoons intersected and surrounded by trees, whether native or exotic. Certainly fruit-bearing species such as Melia are important, but I believe that parts of the reserve would benefit from significant opening up. When I first arrived in HK 20 yrs ago, the reserve was significantly more open than it is now. It also supported greater numbers of duck in the daytime in the winter, though I don't know if these are related.

Geoff
Author: Tony    Time: 19/09/2008 15:36

Having read the discussion above, I have a few opinions on the issue.
Thinning has been widely practiced as a silvicuture tool to accelerate the growth of trees.
A few studies suggested using thinning of exotic trees as a restoration tool to improve plant diversity.
I think whether to chop down exotic trees need scientific evidence to support, yet, NO research has been done in HK
on the effect of thinning exotic plantation to plants/animals.
There is a study in Taiwan (Yuen et al., 2005) study the effect of thinning on short term response of animals communities.
Yuen, H.W., Ding, T.S. & Hsieg, H., 2005. Short-term Responses of Animal Communities to Thinning in a Cryptomeria japonica (Taxodiaceae) Plantation in Taiwan. Zoological Studies 44(3): 393-402.
They suggested that different thinning levels did not show significant effect on abudance and species of small mammals and non-breeding birds. But affect the abundance of ground invertebrate. Opening up forest canopy may increase plant diversity to colonize new niche.

I think all these should be considered carefully. Clear felling must not be possible as it affect microclimate condition and may introduce invasive species like Mikania in the forest. The effect of thinning on birds may not be reflected in short term, say within 5-10 years, as there are other factors affecting species richness and abundance, like food availability.
Ideally, native trees may able to grow larger if a few exotic trees are chopped down, but it takes long time for succession to take place and replace all of the exotic forest.

I think this is worth for discussion and to brainstorm what we can do to improve the biodiversity.
Author: lwingkay    Time: 20/09/2008 11:36

Hiking in Mai Tze Lam and Pondering on from Tony’s

Lately, I spent an afternoon walking up to Mai Tze Lam in Ma On Shan to do some shooting and found that trees there are pretty thick, well grown and mixed in varieties and that they are scattered in a relatively well defined pattern.

First, about the varieties. The commonest species are, in descending order, the acacia, bauhinia and the ivy tree. Scattered ones are: The elephant's ear, lance-leaved sterculia, Chinese banyan, lebbeck, sweet gum, flame of the forest, China berry, rhododendron, queen crape myrtle, sea hibiscus, cotton tree, swamp mahogany and turn-in-the-wind.

About the distribution, it is interesting to see that the acacia spread out evenly along both sides of the uphill trail. To the side of the acacia, the ivy tree is common. Probably, the ivy tree prefers to grow next to an acacia by nature but it is likely that AFCD had planted them together for a certain reasons, e.g. the acacia a good windshield and pretty resistant to fire and their togetherness may serve a long term healthy growth purpose.

The acacia is the king of the forest there. They are tall and their crowns roof the forest, not only that but they also hang their branches out to shade the trail along which they run. If this situation persists, the crowns will make it difficult for the shorter plants below to grow properly. Perhaps, it is worthwhile to do something about it.

About biodiversity of bird species, do have to say that the bulbul, magpie robin, Japanese white eye, spotted dove and sparrows are the commonest. Occasionally, you may see the long-tailed shrike, black-collared starling and black-throated laughing thrust. There must be other species, e.g. the barbet, in the woods, I think, but I doubt that there are birders or officers who have been there to take records of the species deep down there.

We leave the species deep in the woods for the time being. Judging by the species that were seen along and beyond the trail, can we say that the kinds of trees mentioned in the second paragraph are still not good enough for more varieties of species to be possible? Has that been the case because the above bird species are more adaptive to the aforesaid plants species, so we can see them more as a result? Or is it that these bird species are lower in the food chain, so more numerous and discernable? Or can we say that it is because we have not penetrated deep enough into the forest that we fail to identify other species?

I have been thinking if there are archives in Hong Kong that can give us a better knowledge about the state of being in the natural habitats in Hong Kong as well as the situations of biodiversity in there.

Back to Tony's recap from the Taiwanese article he read. Tony said that [the Taiwanese article] suggested that different thinning levels did not show significant effect on abudance and species of small mammals and non-breeding birds [but it affected] the abundance of ground invertebrate. In the first place, it is an interesting finding but my first feeling is its validity to localities that do not resemble Taiwan’s; but evidently, the methods as well as the outcomes are worth looking into. Second, it seems to reflect the kind of picture that I saw from the hiking up Mai Tze Lam: that despite the presence of a variety of plants, the variety of bird species present may not be proportionally at a higher rate. Have to say again that it is an interesting counter-finding but, there must be other cases that are to the contrary elsewhere that we can learn from in planning species thinning locally in Hong Kong.

Back to my feeling about thinning. My stance is: (a) very positive and it has to be done from time to time for better forest management and the equilibrium of growth of different plant species; and (b) positive from the point of view of attracting more bird species because in principle more plant varieties will certainly do birds some good one way or another. However for (b), before thinning, we have to take an account of the bird species in the natural habitat in question to decide whether or not biodiversity problems exist, whether or not thinning is justified from other biodiversity considerations as well as considerations of environmental and forest protection origin.

Regards,
Peter

[ Last edited by lwingkay at 20/09/2008 12:06 ]
Author: wmartin    Time: 20/09/2008 13:04

Briefly:

Good to see further replies n thought.

Yes, a complex issue.

I believe that assessments of insect diversity would be faster ways of better reflecting values of areas of forest (those with good tree variety, inc native species; those with woeful variety verging on monoculture, w non-natives)
Birds, though, v useful and obvious, tho ranges surely mostly larger than many a single species stand.

Species like magpie robin, spotted dove, long-tailed shrike not forest birds: naturally, I'd guess would have been more limited to places where trees fell down, or maybe fires. Man helped these, as sparrows.

Bit surprised re the Taiwan result; I'd figured that thinning paper barks would pretty quickly increase bird divdersity, initially with birds favouring clearings/shrub land.

I've a book by CIFOR (researches forests), on felling in Borneo - bit like reverse of situation we're discussiong, as go from full, natural forest, thro various degrees of felling timber. Initially, most species remain; but eventually, get fewer and fewer forest species, more of the generalists (and lower diversity overall, even if populations of some species pretty high).
In this, woodpecker diversity declined, but not to zero in any plots that weren't clear felled, as I recall. This led to me thinking just how horribly effective Hong Kong's deforestation was.
Author: wmartin    Time: 15/01/2010 23:25     Subject: AFCD to fell some exotic trees and favour native species

Good to see article in yesterday's South China Morning Post, re AFCD having embarked "on a programme that will gradually phase out exotic tree species and replace them with local ones".
Says that at 21 country park sites, exotic species that had been widely planted on barren land after Second World War will be removed to make way for mix of local species.
"Thousands of the trees will be felled this winter, with new species belonging to local species to be planted in spring".

Yippee!

- now if could but get some of the axemen to come over to Cheung Chau, chop down a load of acacias, and replace with some mix of local species, my local patch might see an upsurge in bird diversity...
Author: subbuteo    Time: 16/01/2010 17:35

There are several paper bark trees along the Lam Kam Road in Lam Tsuen, Tai Po marked for transplanting rather than felling.  That seems like a ridiculous waste of time and effort.



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