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There is a sign, at the Eden Nature Park & Resort in City of Davao, Philippines, that says this:

Of concern to all! A tree is worth $193,250

According to Professor T.M.Das of the University of Calcutta. A tree living for 50 years will generate $31,250 worth of oxygen, provide $62,000 worth of air pollution control, control soil erosion and increase soil fertility to the tune of $31,250, recycle $37,500 worth of water and provide a home for animals worth $31,250. This figure does not include the value of fruits, lumber or beauty derived from trees. Just another sensible reason to take care of our forests.

From Update Forestry Michigan State University

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The figure, sometimes incorrectly quoted as $196,250, is cited at various green blogs, and sold on a bright red poster at Singapore Zoological Gardens, but i haven't been able to find the study behind it.

So is a tree living for 50 years worth $193,250?

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Cees Timmerman
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  • Seems a bit too localized... – Sklivvz Apr 26 '13 at 15:58
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    What Nation's currency is that? And when? – Ladadadada Apr 26 '13 at 16:06
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    @Ladadadada Given the attribution to Michigan State University, it seems like (although not certain) that the currency would be U.S. dollars. – Beofett Apr 26 '13 at 16:37
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    Whats with that myth that trees produce the oxygen we breathe? – Stefan Apr 26 '13 at 16:45
  • @Stefan: Sounds like a separate question. – Oddthinking Apr 26 '13 at 16:57
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    Those figures seem to completely ignore that the tree will also be consuming for those 50 years. Additionally if I were to take $50 worth of a liquid antibiotic and mix it with 5 litres of bleach it is no longer worth $50. Even if the amount of Oxygen it produces is worth $31,250 in a pure form that doesn't mean that we can extract that level of value from it. – Ian Apr 26 '13 at 20:54
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    Things can have prices in Economics, as well as costs and benefits to specific individuals. These can vary with the circumstances of time and place (see Hayek, The Use of Knowledge in Society: http://www.econlib.org/library/Essays/hykKnw1.html ). The "true value" of a thing sounds like numerology. It would not be part of a college economics curricula. – Paul Apr 27 '13 at 17:08
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    It sounds like the real claim is "The tree generates X resources in 50 years" which is ENTIRELY DIFFERENT than saying "A tree is worth X." I just threw away a dot-matrix printer which helped me, over the last ~20 years, produce, sell, ship, process several thousands of dollars worth of products. That doesn't mean the printer is worth thousands of dollars. (Unless someone wants to offer me that price--I'll go dig it out of the trash). *A tree is worth what someone will pay for it.* – Flimzy Apr 27 '13 at 23:18
  • A tree is worth whatever is the going rate for timber or firewood, whichever is higher. – jwenting Apr 29 '13 at 06:10
  • @jwenting: Usually a combination of the two. Different parts of the tree have different commercial values. And some trees' primary commercial value is aesthetic (landscaping, etc), which makes determining the value of a mature tree difficult (since they can't typically be bought). – Flimzy May 01 '13 at 22:06
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    With a few exceptions (such as the desert southwest), most suburban USA properties have a lawn with one or more trees. If each tree were worth $193,000, then the current financial crisis in real estate could be easily solved by homeowners simply refinancing or selling trees. If that solution sounds like nonsense, so is that high appraisal of the value of a tree. – Paul May 02 '13 at 02:19
  • @Flimzy true, though I'd say that value can be bought by buying a new tree from a grower for a few hundred Dollar/Euro at most for most trees (not counting very old ones). The transport and planting may well cost more than the purchase price of the tree itself (and goes up as the tree gets larger, until you need a large crane for that old tall oak you bought because you wanted a fully grown 20m tall tree with a 2m circumference in your newly planted garden). – jwenting May 02 '13 at 05:41
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    I can't believe we are still discussing this, given we all seem to agree. There is a difference between the price of a tree and the value of a tree to a person, which is why people buy things. There is a difference between the price of a tree, and the economic or ecological value. There is a difference between the economic value of the oxygen provided by a tree and the price of bottled oxygen. There's a difference between the value of a tree and the value of the lumber from a tree. All this is clear. This claim attracted attention because it confounded these issues. What more is there to say? – Oddthinking May 05 '13 at 14:01
  • We don't even know how much is $193,250 (what currency, what rate). The sign is only for homo economicus, a measure like that cannot be scientifically proved because the perspective is flawed. Take that sign as an advertisement, not a scientific-based statement. – chirale May 19 '13 at 07:10
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    @chirale See my answer. The quoted currency is in Singapore dollars. – denten Jul 21 '13 at 02:23

2 Answers2

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Nancy Beckham explains in Trees: finding their true value about how the valuation was done.

It was published in Indian Biologist, Vol XI, No. 1-2, 1979, by T.M. Das, a journal which is edited by... T.M. Das.

Prof Das's system looked at a number of factors, one of which was oxygen production. The net accumulation of one gram of carbon in a tree was compared with the net production' of 2.66 g of oxygen. This oxygen production was related to the weight of a tree, using a correction factor for the amount of leaf shed every year and the age of the tree. The oxygen was valued at the prevailing Indian market rate.

Of course, what its components would be worth (or rather what its outputs are worth) in its purest form is a nonsense method of valuing anything.

There are various ways of defining economic worth, but it is clear that none of them are going to value a average, unspecified tree at $193,250, when its replacement and market price cost is so much lower. On the other hand, particular trees may be valued at higher than that price.

Oddthinking
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  • Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/52106/discussion-on-answer-by-oddthinking-is-the-value-of-a-tree-193-250). – Oddthinking Jan 20 '17 at 02:10
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David Bennett from the Aboriginal and Torres Strait Islander Commission has a great article on this topic in Tropical Rainforest Research, under the title of "Valuing a Tree: The Ethics of Environmental Evaluation." The gist of it is that converting trees to currency is not an exact science. A number of assumptions could go into such a calculation, producing a range of values.

Bennett quotes the exact number from T.M. Das (in Singapore dollars by the way, which converted to US currency comes out to $158,739 / 50 years). About this metric he writes,

This method is crude, of course. It indicates only an average functional value for a hypothetical tree. The functional value of a given tree of a given species may be more or less than this amount. The point remains that the economic value of a tree cannot be reduced to its materials.

By comparison, an article in the Journal of Arboriculture 29(2): March 2003 indicates that the city of Davis, California

maintained nearly 24,000 public street trees that provided $1.2 million in net annual environmental and property value.

By this measure, a tree brings 50$ per year, and $2,500 over 50 years. The value in this study includes: "electricity (kWh/tree) and natural gas savings (kBtu/tree), atmospheric CO2 reductions (kg/tree), air quality improvement [NO2, PM10, and VOCs (kg/tree)], stormwater runoff reductions [precipitation interception (m3 /tree)], and property value increases [∆ LSA (m2 /tree)].

If I was wanting to be precise about the numbers, I would at least quote a range between these two estimates.

denten
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    and how much does it cost that city to plant, water, prune, and replace those trees? I know the city I live spends a lot of money on that (well, not so much watering as I live in a rather wet climate). Don't have figures, but wouldn't be too surprised if that came close to the $50 per tree per year figure, especially given the wastefulness of typical government agencies. – jwenting May 01 '13 at 07:10
  • Agreed. The Arboculture article provides a much more detailed estimate than that of Das. – denten May 03 '13 at 17:40
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    @jwenting, denten quoted a net profit, so labor is already paid. – Cees Timmerman May 16 '13 at 09:52
  • @DuckTapeAl fixed – denten Feb 09 '17 at 22:04