열대우림에서 지속가능한 벌목은 불가능하다

Industrial logging in primary tropical forests that is both sustainable and profitable is impossible, argues a new study inBioscience, which finds that the ecology of tropical hardwoods makes logging with truly sustainable practices not only impractical, but completely unprofitable. Given this, the researchers recommend industrial logging subsidies be dropped from the UN's Reducing Emissions from Deforestation and Forest Degradation (REDD+) program. The study, which adds to the growing debate about the role of logging in tropical forests, countersrecent researchmaking the case that well-managed logging could provide a "middle way" between conservation and outright conversion of forests to monocultures or pasture.

"We are facing a global biodiversity and a climate change crisis and we cannot afford to continue to lose primary tropical forests—they are central to resolving both crises," authors Barbara Zimmerman with the International Conservation Fund for Canada and Cyril Kormos, Vice President for policy with the WILD Foundation, told mongabay.com. "Despite decades of trying to log sustainably, the rate of deforestation has barely dipped over the last 20 years, from 15 million hectares per year to 13 million hectares per year—and these are low estimates. Industrial logging has shown no capacity to keep forests standing. on the contrary, logging is usually the first step towards total clearing to make way for agricultural use."

The study found that just three rounds of logging in tropical forests resulted in the near-extinction of target trees in all major rainforest zones—South and Central America, Central Africa, and Southeast Asia—resulting not only in ecological disturbance but economic fallout.

Ecological and economic barriers

Deforestation for palm oil in Sabah, Malaysia. Often logged forests are then converted to plantations or pastures. Photo by Rhett A. Butler.

The very ecology of tropical rainforests—their rich biodiversity, unparalleled variety, and hugely complex interconnections between species—makes them particularly susceptible to disturbance. Targeting only a few key tree species in the forest, loggers quickly plunder these species while leaving the rest standing, rapidly changing the overall structure of the ecosystem. In this way, loggers undercut the very ecological system that allows their favored trees to replenish.

"Virtually all currently high-value timber species, are exceptionally long lived and slow growing, occur at low adult density, undergo high rates of seed and seedling mortality, sustain very sparse regeneration at the stand level, and rely on animal diversity for reproduction, all of which point to the conclusion that tropical trees probably need very large continuous areas of ecologically intact forest if they are to maintain viable population sizes," Zimmerman and Kormos write in their paper.

The particular ecology of these trees has resulted in most logging companies simply entering a primary forest, cutting all high-value species, and then leaving it to colonizers or razing everything for cattle pasture or monoculture plantations (such as pulp and paper, rubber, or palm oil).

"Logging in the tropics follows the same economic model as is evident in most of the world’s ocean fisheries," Zimmerman and Kormos write. "The most-valuable species are selectively harvested first, and when they are depleted, the next-most-valuable set is taken, until the forests are mined completely of their timber."

Boom and bust. Sawlog and veneer-log production for the Solomon Islands and five key South-East Asian nations (derived from FAOSTAT, 2011). Courtesy ofShearman et al 2012.

While initial logging can be quite profitable, later harvests bring in less-and-less money: fewer target trees can be found and the regenerative process for such species is compromised overall. Eventually industrial logging kills itself, leaving an economic vacuum that in accessible areas is often filled by conversion to pasture land, oil palm estates, industrial agriculture or timber plantations.

Some scientists have argued that the solution to this problem is to inject sustainable forest management practices into logging companies in the tropics. According to these sustainability proponents, this would ensure harvests over the long-term while protecting overall forest health.

Impact of various disturbance regimes on biodiversity in tropical forests. Chart based on Gibson et. al 2011. Photo by Rhett Butler. Click to enlarge

But according to their paper, even so-called reduced-impact logging—which is currently the exception rather than the norm in the tropics—considerably changes a forest's ecology. With many of the forest's vital seed and crop trees cut, Kormos and Zimmerman point out that "low-impact" logging leaves 20-50 percent of the canopy open, when "even small openings in the canopy (5-10 percent) can have significant impacts on the moisture content in the forest and increase risk of fire." Debris left on the forest floor quickly dries out, creating perfect fodder for fire. Unlike temperate forests, fires in primary rainforests are almost unheard of, but low-impact logging creates a new set of ecological conditions that leave the forest vulnerable to heat, wind, and, yes, fire.

"We now know that under the present sustainable forestry management guidelines, tropical forests left to regenerate naturally will be composed largely of light-wooded tree species of no to low commercial value, whereas dense-wood, high-value timber species will experience severe population declines," Kormos and Zimmerman write, noting that current guidelines are far too lax to keep forests intact.

True sustainability is not impossible to achieve, write Zimmerman and Kormos, but guidelines would need to be considerably toughened. Forestry companies would need to cut only every 60 years or more, harvest less than five trees per hectare, leave smaller logging gaps in the canopy, avoid cutting young trees, and use siliviculture techniques to plant new seedlings, among other considerations.

Giant rainforest tree in Sumatra. Photo by Rhett A. Butler.

"The key to a forest’s ability to recover most of its original attributes after selective logging is low harvest intensity," they write.

But, there is a reason why there are no industrial loggers in the tropics putting such stringent rules in place.

"The problem with implementing this kind of protocol is that it would substantially diminish harvestable timber volume while further increasing management and training costs, which would make the timber operation economically unviable," Zimmerman and Kormos told mongabay.com.

It's no wonder then that logging companies generally cut-and-run, a practice which has resulted in loggers moving from one untouched tropical forest to the next, always looking for the short-term gain. For example, after logging out most of the forests in Borneo, loggers moved into places like Sumatra. Now that Sumatra has been devastated—with many of its forests turned into monoculture plantations—industrial logging went to New Guinea and the Solomon Islands. Primary rainforest is vanishing worldwide.

Logging not a "middle way"

Zimmerman and Kormos’ paper is one among several that debates, sometimes heatedly, the role of logging in protecting or destroying tropical forests. For example, a paper inConservation Lettersrecently came to a very different conclusion than Zimmerman and Kormos, describing well-managed logging as a middle way between conservation and outright destruction of tropical forests for agriculture or ranching.

"Selectively logged tropical forests, especially if they are logged gently and with care, retain most of their biodiversity and continue to provide ecosystem services such as carbon sequestration and hydrological functions," lead author of that study, Francis Putz with the University of Florida told mongabay.com in May.

Raw logs waiting for transport in Guyana. Photo by Jeremy Hance.

Putz's paper did not argue that logging had no impact, but rather that any impact from logging was far preferable than clearing a forest entirely. While Kormos and Zimmerman agree with this point, they see a different remedy.

"There is no question that industrial logging is better than cattle pastures or oil palm or other plantations—but the fact that industrial logging is better than total forest conversion doesn’t mean we should subsidize it," Zimmerman and Kormos told mongabay.com. "Subsidies should be directed towards activities that maximize carbon, biodiversity and social benefits."

They also say some of the paper's findings are problematic. "The article includes introduced species in the biodiversity totals, and the biodiversity surveys cited were all done soon after logging and before a second harvest, so there would be an expectation that there would still be biodiversity left in the short term—the question is what happens to biodiversity in the medium term, in particular after a second harvest? In addition, the article states that a logged forest retains 76% of its carbon. But 24% of a forest's carbon is a very substantial amount of carbon emissions—it could take several decades just to recapture that carbon, whereas we need to be maximizing forest carbon right now."

Even more importantly, perhaps, is that economic problems remain, dooming many logged forests to total clearance.

"The 'middle way' does not make logging sustainable. The Putz et al article clearly acknowledges that the middle way does not achieve sustained timber yields. As a result, it does nothing to change the fundamental dynamic, which is that logging usually precedes conversion to higher value agriculture use. So the 'middle way' could actually make things worse—accelerating forest conversion," Zimmerman and Kormos say.

REDD-out

Aerial view of logging roads in Malaysian Borneo. Photos by Rhett A. Butler.

Given the problems of balancing the ecology and economics of logging in tropical forests, Zimmerman and Kormos argue that the UN program, REDD+, should discontinue a component that would give money to industrial logging companies to manage rainforests for their carbon.

"REDD+ should not be used to subsidize industrial logging. The biodiversity and climate change crises are rapidly getting worse, and keeping primary forests intact is an essential part of the response to both crises. REDD funding should be reserved for activities that keep primary forests intact, such as community management and protected areas" Zimmernam and Kormos say. They note that REDD+, which is meant to pay countries to preserve forests as carbon reservoirs, would undercut its main goal, since even well-managed logging concessions lose significant carbon when trees are felled, especially large, old trees. In addition, logged forests are at significant risk of total carbon loss as a result of fire or conversion to agricultural use.

Still, Zimmerman and Kormos, say logging can occur in tropical forests, only it should not be small operations run by local communities, and not the industrial logging that dominates the trade today.

"Community logging works when it is implemented at non-industrial scales by communities that have a vested interest in being good stewards of their land," they say. The key here is that local communities govern their own forests, which takes away the cut-and-run problem. In addition, such programs must be supported by the national government. This is where REDD+ could really make a difference.

"The most important reason that these successful local-scale sustainable forestry management models have not been scaled up to secure the world’s remaining tropical forests is a lack of funding—-a situation that REDD+ investment might correct," the authors note.

Zimmerman and Kormos say they would support a global moratorium on industrial logging in primary forests, an idea that has been floated in some environmental circles. Smaller-scale moratoriums are not unprecedented. Indonesia is currently attempting to implement a national moratorium, albeit the scheme is facing many difficulties and criticism both from environmentalists and industry. In addition, in 2002, the Democratic Republic of Congo instituted a moratorium on any new logging concessions being granted or renewed, although this moratorium has also suffered from widespread breaches. But if loggers are not to enter the world's last primary tropical rainforests—those, at least, currently unprotected by parks—drastic changes would need to be made in forest governance, which currently favors big industrial logging conglomerates over local communities with a long-term stake in the health of their forest.

Gabon. Photo by Rhett A. Butler.

CITATIONS:

Barbara Zimmerman and Cyril Kormos. Prospects for Sustainable Logging in Tropical Forests. BioScience 62: 479–487. doi:10.1525/bio.2012.62.5.9.

Francis E. Putz, Pieter A. Zuidema, Timothy Synnott, Marielos Peña-Claros, Michelle A. Pinard, Douglas Sheil, Jerome K. Vanclay, Plinio Sist, Sylvie Gourlet-Fleury, Bronson Griscom, John Palmer and Roderick Zagt. Sustaining conservation values in selectively logged tropical forests: The attained and the attainable. Conservation Letters. 2012. doi: 10.1111/j.1755-263X.2012.00242.x.

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