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How tree huggers can save forests with science

While hugging a tree sounds relaxing, it’s harder than you might think - especially when the tree is 20 storeys high and 3 metres wide, it’s hot as hell, and you’re swatting away swarms of sweat bugs…

Using tree measurements by Papua New Guinean villagers such as Daniel and Jackson, scientists can estimate that this tree stores about one tonne of carbon in its trunk and branches. Michelle Venter

While hugging a tree sounds relaxing, it’s harder than you might think - especially when the tree is 20 storeys high and 3 metres wide, it’s hot as hell, and you’re swatting away swarms of sweat bugs.

But there’s a hard-headed reason behind that tree-hugging work: you can’t properly manage what you don’t measure.

Lack of reliable information about so much of the world’s forests is part of why we’re still losing forests so fast. Deforestation contributes an estimated 10-15% of all human-caused greenhouse gas emissions. Forests and the clouds of water vapour that they produce also help to cool the planet.

But without an army of scientists, how can we do a better job of counting the trees and carbon in our forests? We decided it was time to test if the locals could put scientists out of a job - and it turned out we weren’t alone.

Why bother counting tree carbon?

Half of a tree’s dry weight is made up of carbon. Using simple field measurements, such as girth measured at 1.3 metres above the ground, is the surest way without cutting the tree down to estimate its weight and its value in locked-up carbon.

It’s labour-intensive work for scientists like us in muddy boots, measuring hundreds of trees in each hectare, usually in remote, logistically challenging terrain. And all of that makes it an expensive process, and therefore hard to do on the scale we need to properly account for the carbon value of our forests.

Fortunately, we’re also getting better all the time at measuring forests from space using satellites. Only last week, a team of US researchers (including from Google) published the first high-resolution global map of the world’s forests, which revealed that we are continuing to cut down forests around the world much faster than we’re regrowing them.

Published in the journal Science, the map is made up of more than 650,000 satellite images, making it possible to search for particular locations and then zoom in down to a 30-metre resolution to see where forests have been lost (shown in red) or gained (shown in blue).

But for the most reliable results, counting trees and the carbon stored in them requires old-fashioned sweat and techniques used for a century.

Growing money from trees

One of the ways that it’s possible to make money by leaving forests standing is through the United Nations' Reducing Emissions from Deforestation and forest Degradation program REDD+, which aims to reduce forest carbon emissions in developing countries by paying to preserve to the carbon stored in these forests.

But that’s easier said than done. When REDD+ was first framed in 2007, it was heralded as “the most promising opportunity for reducing deforestation, conserving forests and contributing to climate change mitigation”. Now, enthusiasm for the policy has dwindled.

The UN program has largely stalled due to stringent Monitoring, Reporting and Verification requirements, that are beyond the capacity of most developing countries.

Unfortunately less than 10% of the 99 developing countries eligible to be part of the REDD+ scheme have the in-house expertise or the resources to employ outside experts to conduct such field inventories. As a result they cannot reap the economic benefits of protecting forests.

The idea of bridging this gap by engaging forest-dependent communities to monitor carbon in their own forests has become more popular. But can local people collect data reliably, matching the kind of results that scientists get to meet the stringent Monitoring, Reporting and Verification requirements?

Can locals beat scientists at their own game?

Our team of scientists spent seven months in the YUS Conservation Area on the Huon Peninsula of Papua New Guinea, a rugged, road-less mountain region where people depend on their forest for building material, food and fuel.

The participants in our study live in three of about 30 communities that have achieved a remarkable milestone for conservation.

Collectively these PNG communities have pledged 74,000 hectares of primary forest to protect the endangered Matschie’s tree-kangaroo from overhunting.

The Matschie’s tree-kangaroo is the largest animal in this forest and was previously threatened by overhunting. But in 2009 villagers pledged to protect the important cultural icon. Mark Ziembicki (with permission)

In 2009, the YUS Conservation Area became the first (and only) area protected under the PNG’s Conservation Area Act 1978. Thus, not only can community-led forest monitoring provide local livelihoods in exchange for forest protection, it will help ensure the protection of endangered species into the future.

The 12,000 villagers in the YUS area currently have limited options for earning a wage. There is therefore a risk that they will resort to the old school livelihood options provided by extractive industries at the cost of inevitable environmental degradation and cultural dislocation.

We trained six member teams from three communities to perform forest-carbon assessments using survey tapes, GPS units and laser-rangefinders. None of this equipment had been previously encountered by the villagers.

These teams then undertook self-led forest-carbon surveys in 41 randomly selected survey plots. Once the community surveys were complete, we spent three months re-measuring the same plots. We double-checked all 4211 field measurements recorded by the community teams from lowland forest at 50m altitude to cloud forest at 3000m.

Our results confirm that, with only three days of training in unfamiliar and complex techniques, people with little formal education can produced real-world field data as reliably as experts.

And in some instances, communities performed better than scientists. For example, marking out a rectangular plot area is a difficult task in dense forest on steep terrain and plot area was more accurate in the community surveys. This may seem trivial, but errors in plot area are directly proportional to errors in final carbon estimates.

Flying into the YUS Conservation Area, Papua New Guinea, to measure forest carbon.

We further found that the biggest source of error in forest-carbon estimates is from imprecise measurement of large trees. Though trees of more than 50cm in diameter only constitute 14% of the trees measured, these trees were responsible for 85% of the total error in forest carbon estimates.

Community results with global significance

We’re currently preparing our findings from PNG to submit to a peer-reviewed journal. But our results have since been independently backed up by an international group led by Finn Danielsen, published in the latest edition of the journal Ecology and Society.

Their study - which was the first-ever quantitative study of REDD+ community participation - demonstrated that local people from Indonesia, China, Laos, and Vietnam using simple tools like sticks and ropes could generate forest-carbon data on par with professional foresters using high-tech devices.

The study also found that nearly half of REDD+ projects still don’t work with communities in gathering data on forests. So there is huge, untapped potential for local communities to earn money from protecting their forests, rather than that REDD+ funding ending up with outsiders.

As the latest UN climate talks in Warsaw come to a close, with little sign of major progress, this is at least a glimmer of hope.

For communities considering whether to forego cutting down their forests, locally-led forest monitoring offers a potential win-win-win for people, forests and our climate.

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18 Comments sorted by

  1. John Newlands

    tree changer

    Charging carbon credits to preserve a standing forest is misconceived. It's akin to demanding money not to break a window. The standing forest is not a new carbon sink since net carbon flows are the same before and after money changes hands. For the forest owners (probably not the inhabitants) it's money for nothing and for the emitters it's a small price to get off the hook. Other things being equal atmospheric CO2 is unchanged.

    It would be particularly wrong if Australia paid Indonesia…

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    1. Michael Bird

      Professor, geochemistry and environmental change at James Cook University

      In reply to John Newlands

      I think the analogy is more 'poacher turned game keeper'. We are (I presume) mostly happy see payments to local people to act as guards to protect elephants in conservation areas in developing countries. If these payments were not made the need to make a living would see many of these people return to poaching and we'd have less elephants as a result.
      Whether these forests will sequester carbon over time depends very much on their disturbance history, but in this instance it is less important to build up carbon as to not have it lost through logging for economic gain.

  2. John Newton

    Author Journalist

    Wonderful story and congratulations on what is, as you say, a glimmer of hope. Most heartening is the local participation. These are the people who will suffer from the wrong-headed stubbornness of the deniers.

  3. Paul Prociv

    ex medical academic; botanical engineer at University of Queensland

    Fascinating, and very important work. But, just a tiny, pedantic quibble: "swatting away swarms of sweat bugs and malaria-laden mosquitoes" is not quite correct. Malaria-carrying mosquitoes feed only between dusk and dawn, not in the daylight hours when, I presume, this sort of work is done. Regardless, your daytime-feeding mossies could readily inoculate you with myriads of other pathogens, notably viruses.

    1. Liz Minchin

      Queensland Editor at The Conversation

      In reply to Paul Prociv

      Paul, I'll take responsibility for that - I asked the authors what kinds of things they had to deal with while doing this field work and when they mentioned sweat bugs & malaria mozzies, I suggested a colourful intro that gave a sense of what the work involved...

      One of the things I love about The Conversation is that we have smart readers/commenters who do question the content of articles, so am very happy to take feedback like this. Pedants who make articles even more accurate are welcome.

      I'll take out the mozzies now. Sweat bugs alone sound unpleasant enough.

  4. Peter Boyd Lane


    Great article, but I can't share the optimism. During the 90s we were accused of being emotional. Since then we have been VERY scientific to demonstrate that logging our forests is unsustainable and very damaging. To that we have added irrefutable economic argument that we lose money by logging our forests (in 2012 the WA govt gave $72 million to its logging "enterprise" and got nothing in return. In 2013 logging native forests in WA was done at a $21 million loss. It can be shown that losses since 2000 amount to almost $100 million). But, as in WA, governments around Australia keep on logging.

    1. Mark Poynter


      In reply to Peter Boyd Lane

      It is disappointing (but seemingly almost inevitable) that an article about tropical forests can spawn misinformed comments about the Australian situation.

      Firstly, only about 5% of Australia's forests and woodlands are being managed for wood products, so, even if the available timber resource in this area was being unsustainably harvested as you are claiming, there is another 95% of our forests that are not even used. I suspect the situation is quite different in tropical countries where corruption…

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    2. Murray Webster

      Forestry-Ecology Consultant/Contractor

      In reply to Peter Boyd Lane

      Must say I am very wary of transferring concepts from tropical Rainforests in PNG to Australia's Eucalypt forests.

  5. Des Stackpole

    Post hole Digger

    I'd like to see a few village scale examples of REDD money in the hands of the villagers, alongside what they promised or achieved or did (forest inventory?) to get it.

    1. Dianna Arthur


      In reply to Michelle Venter

      Thanks Micehlle

      It is responses such as this, that place TC above the rest of independent media.

  6. David Cameron

    logged in via Facebook

    Congratulations on this article. Tree volume and biomass measurements are time consuming and demanding and to involve local people in carrying this out is excellent. Our group with CSIRO were involved in biomass and nutrient measurements of small trees to establish the most efficient methods so that key parameters were selected for optimum data collection and interpretation. We did not involve local people in this - even other forestry workers probably thought we were quite mad. We were also working with plantation trees and measuring sample trees for leaf area, nutrient content and wood density. All very interesting and even after the research was halted 22 years ago, my colleague and I are still attempting to write papers for publication in the scientific literature.

  7. James Hill

    Industrial Designer

    Is there something missing from the caption, to the first photograph, which suggests that only "one tonne" of carbon is captured in that large tree?
    Other studies suggest that if each individual on the planet sequestered about eight tonnes of carbon then the over supply of carbon dioxide might be ended.
    What sort, size of tree, for example, might allow an individual to claim to have sequestered such an amount of carbon?
    And since the tree has an identity and an address which can be monitored…

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  8. Ray Alok

    logged in via Facebook

    Great read, as an observer from PNG its fantastic to see progress on some REDD+ activities in the country. As the article recognized sustainability of said activities in PNG is only through equitable landowner participation, and so the work at YUS certainly represents 'many steps' in the right direction.

  9. Pamela H.

    logged in via email

    As one of our childhood flippered friends once said: "It's not easy being Green".

  10. Murray Webster

    Forestry-Ecology Consultant/Contractor

    Hi Michael, Great work.
    Foresters developed these measurement techniques decades ago and there is a huge body of literature dealing with error and how to address it.
    I assume you know of Airborne Lidar (aka Airborne Laser Scanning)? Foresters are now leaning toward Lidar in estimating timber volume and biomass (CO2). With this tool we can measure the height of all canopy trees in a forest with an accuracy greater than what can be achieved with diameter tapes and range-finders. Studies regularly eported r2 values in excess of 0.9 for biomass. However I guess no-one has the money for that. Though I am working on a research project where we are looking at updating height growth with automated processing of aerial which is much cheaper than Lidar.