Is there a deforestation limit we can aim for?

Deforestation is bad, according to just about everybody in the world who isn’t actively engaged in cutting down a tree right now. It isn’t a controversial position to say that we should save our rain forests and other major wooded areas, but it also isn’t a particularly useful one. A more interesting question to answer is exactly how much is too much when it comes to deforestation: Just as the world has coalesced around doing our best to hold global warming under two degrees C from preindustrial levels, is there some amount of forest that we really must keep in order to keep the ecosystems at least somewhat intact?

A group of researchers in Ecuador and Germany set out to determine that limit in the tropical Andes region in South America, at least in terms of how forest cover affects “benthic” indicators—essentially measures of how healthy a river or stream is based on the water, sediment, animals living there, and other factors. Specifically, they looked at 23 streams in two separate “headwater catchments” of the Zamora River basin, in Ecuador; one of the two is heavily populated and has been heavily deforested, while the other is a more sparsely populated and less disturbed area. “In Ecuador, deforestation for agriculture and/or urbanization is a critical threat for Andean ecosystems, reaching annual deforestation rates of 2.7 percent between 1989 and 2008 in the montane forests of southern Andes,” they write. So how does that sort of rate change what’s beneath the canopy?

Over the full catchment area, they found that water quality is significantly better when vegetation cover is above 70 percent, giving us one large-scale line it seems good not to cross. That line also holds true for “macroinvertebrate community assemblages,” or groups of animals that would include larval insects, snails, crustaceans, and other such critters; above 70 percent vegetation coverage again, those communities were more diverse. Of 53 genera of macroinvertebrate found in areas with at least 70 percent coverage, an amazing 25 of those were absent from the more deforested areas.

There was some correlation with water quality and macroinvertebrate success at a smaller “riparian” scale, encompassing 30 meters on each side of the stream for its full length, but at an even smaller, local scale the connections broke down.

This is a useful line to know, though of course the specifics may vary based on where in the world one is trying to conserve. And we do need these types of studies in order to define those lines; as it stands, there really isn’t a goal other than to stop pillaging the forests in general. The authors note that in Ecuador in particular, the “constitution defines the right to water and promotes the protection, restoration and management of basins and water resources; but it does not mention how much forest needs to be retained in a catchment or a recommended width for riparian buffers.” Even with the best of intentions, we aren’t sure what we need to save. This is a good—though early—step toward fixing that problem. - Dave Levitan | August 26 2014

Source: Iniguez-Armijos C, Leiva A, Frede HG, et al (2014). Deforestation and benthic indicators: How much vegetation cover is needed to sustain healthy Andean streams? PLoS One, 9 (8) e105869. DOI: 10.1371/journal.pone.0105869

Image: shutterstock.com, Markuso

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  • Prabhat Misra August 29, 2014 at 8:38 pm

    The research article, “Deforestation and Benthic Indicators: How Much Vegetation Cover Is Needed to Sustain Healthy Andean Streams?,” by Carlos Iñiguez–Armijos et al is an important study and will be of great use in controlling deforestation and aware people at grass root level.

    An estimated 18 million acres of forest are lost each year, according to the United Nations’ Food and Agriculture Organization. The causes of deforestation are industrial agriculture, shifting cultivation, urbanization, population growth, desertification, selective destruction and habitat destruction. According to IUCN’s Red List, habitat destruction is universally the most dominant threat to biodiversity.

    This situation will increase deforestation and will disturb Oxygen evolution and Carbon di-oxide consumption ratio in the ecosystem; it will ultimately add to Climate Change. It is estimated that about 15 percent of all greenhouse gas emissions are the result of deforestation. Without remedial measures, the current living “biological life forms” will collapse.

    According to University of Michigan’s Global Change Curriculum, it is only after more than 100 years that forest become as they were before the cut [http://www.globalchange.umich.edu/globalchange2/current/lectures/deforest/deforest.html ].

    According to UNEP’s Millennium Ecosystem Assessment, “Over the past 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fiber and fuel. This has resulted in a substantial and largely irreversible loss in the diversity of life on Earth.”

    Recently, In Africa, Ebola is spreading fast in those countries where deforestation is on peak; there, human activity is driving possible hosts of Ebola virus, bats and wild animals, to find new habitats among human populations.

    We are on the verge of collapsing world ecosystem i.e. biome, due to anthropogenic activities.

    We are facing ” Anthropogenic Climate Change.” By the year 2100, it is estimated that average global temperatures will have risen by 1.0–3.5 °C. We need a strong and most active “GHG Sink system” to achieve 350 ppm CO2 level in the atmosphere. Trees are “Best Natural Sinks of CO2″ and will be helpful to tackle with Climate Change and biodiversity loss.

    Recently, on 23 August 2014, students of Elgin High School, Elgin, USA, participated in a grass root level movement of India, “RED TAPE MOVEMENT,” to save biodiversity and trees [ http://tmblr.co/ZeQ5Pu1PQ0Tk- ]. These students actively participated in Red Tape Movement, in their Elgin school campus [ http://www.dailyherald.com/article/20140815/news/140818960/ ]. This movement is run by me and is helpful to save and increase “GHG Sink system” of the Earth.

    The recent research article and work by the team of great scientist Carlos Iñiguez–Armijos will be helpful in framing international policies regarding biodiversity and forest conservation and in controlling the depletion of natural ecosystems. It will increase “GHG Sink system.”

    Great study.

    Regards,

    Prabhat Misra
    Assistant Director- National Savings
    District- Etawah, Uttar Pradesh, India/
    Founder of “RED TAPE MOVEMENT”
    http://www.twitter.com/redtapemovement
    http://www.twitter.com/prabhatmisra
    http://www.facebook.com/prabhat.lovepeaceunity

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