How Old Is That Tree?

How can you tell how old a tree is without chopping it down and counting its rings?

It turns out that there's some really simple math that you can use to estimate the age of a tree. All you need to know is how big around its trunk is and what kind of tree it is!

Here at Political Calculations, we build tools to solve problems like this! And, after a quick Internet search, we discovered that no one else appears to have already built a tool to solve this kind of math, which means that we'll have a monopoly on tree age calculators on the World Wide Web! Can fame and riches be far behind? Or an intensive investigation by the anti-trust division of the Department of Justice?

Bring it on, we say! Now, let's get to business....

In our tool, enter the circumference of the tree you measured and select which kind of tree it is from our list (if it's not in the list, select a tree that you believe would have a similar growth factor). Then click the "Calculate" button, and we'll give you a pretty good estimate of the age of that tree!

Tree Data
Input Data	Values
Trunk Circumference [inches]
Tree Species	Ash, Green Aspen Basswood Birch, River Birch, White Cherry, Black Cottonwood Dogwood Elm, American Hickory, Shagbark Ironwood Linden Maple, Red Maple, Silver Maple, Sugar Oak, Pin Oak, Red Oak, White Redbud Walnut, Black

Approximate Age of Tree
Calculated Results	Values
Estimated Age [years]

Arboriculturist Jim Skiera offers the following insight for interpreting the results of the math:

"The figures in the chart are taken for forest grown trees. In a landscape setting, where trees are being provided additional care, these figures probably would need to be adjusted to get an accurate estimate. Growth has to do with the location of the tree and the type of care it has received. Trees in the landscape tend to grow faster and develop wider growth rings more quickly because the competition from other trees is usually less and the additional water and fertilizer that is provided by the home owner will also increase growth.

In other words, you need to take into account where the tree you've measured is located. If the tree whose age you're trying to estimate is in your yard or in a park, and not in a forest, our tool will overestimate the age of the tree.

Now for the really cool part. What we've just done for estimating the age of trees, we can do with people too! We'll explain more soon....

Which Species Should You Save?

Suppose, for a minute, that you were in charge of the global organization to preserve endangered species of rhinoceros, of which the two species most at risk of extinction are the Javan rhinoceros and the Sumatran rhinoceros.

Unfortunately, because there is a long list of other species preservation efforts that your fellow environmentalists prefer to support, your organization's resources for preserving these species are limited. So much so that dividing your limited resources between efforts to preserve both species simultaneously will not be sufficient to halt their respective declines in numbers. But, if you threw all your efforts behind preserving one of these species of rhinoceros, you might be able to make a critical difference in its future.

But which one should you choose?

The answer is you should choose to put your limited resources behind the species with the more viable population.

By that, we mean the species whose numbers have not diminished to the point where a random catastrophe, such as a hurricane or tsunami, would be capable of causing their extinction.

Choosing between the species then comes down to the numbers, the math for which has been worked out in a 2011 paper by Gopalasamy Reuben Clements, Corey J.A. Bradshaw, Barry W. Brook and William F. Laurance, describing the SAFE index, which uses a threshold population target to measure how threatened a species may be.

The Species' Ability to Forestall Extinction (SAFE) index measures the relative threat faced by various species, incorporating the best estimates of the species' total population within its known range and its Minimum Viable Population figure - the minimum population needed for it to last over the long term while sustaining its evolutionary potential, which perhaps might better be described as avoiding problems that come from excessive inbreeding within too small a population.

Our tool below is built using the math presented in the researchers' paper. The default data applies for the Sumatran rhinoceros:

Species Population Data
Input Data	Values
Estimated Population in Known Range
Minimum Viable Population

Species' Ability to Forestall Extinction
Calculated Results	Values
SAFE Index Score

Using this math, the researchers found that if a choice needs to be made between preserving the Javan rhinoceros or the Sumatran rhinoceros, the choice should be made in favor of the Sumatran rhinoceros, whose SAFE index score was -1.36 as compared to the Javan rhinoceros' lower score of -2.10.

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Then again, to bring other species conservation efforts into the discussion, they find that "donors with limited resources may want to channel their conservation efforts toward the tiger, a species at the "tipping point", with a SAFE index of -0.21.

We found the SAFE index interesting because it appears to provide a better indication of a species' viability than the percentage of range loss measure that is often used to determine the relative threat of extinction to various species.

But what really sets it apart for us is that this method of prioritizing species recovery efforts would seem to also reflect the actual choices made by the combination of individuals, scientists, lawmakers and organizations seeking to preserve various species, which have consistently put more funding to work in support of preserving species that are only "threatened" as compared to those that are "endangered".

Perhaps that's because they implicitly recognize that this approach is the only one that provides any real chance for success. Because if success can be obtained for one threatened or endangered species, it can then free up limited resources to aid the recovery of other species as well as provide the real knowledge for how that goal might be achieved. It's the snowball effect for paying down debt applied to the problem of conservation.

That's something that upsets many environmental activists, who argue that people must sacrifice their interests in ever greater shares to achieve the activist's goals - whether they can reasonably be achieved or not. But then, since so many of these individuals have such different priorities from most people, it's probably better to stick with the current, imperfect system that has evolved over time, as it somehow seems to work.

References

Gopalasamy Reuben Clements, Corey JA Bradshaw, Barry W Brook, and William F Laurance. 2011. The SAFE index: using a threshold population target to measure relative species threat. Frontiers in Ecology and the Environment 9: 521–525. http://dx.doi.org/10.1890/100177. November 2011. [Note: Ungated version available.]

Restani, Marco and Marzluff, John M. Funding Extinction? Biological Needs and Political Realities in the Allocation of Resources to Endangered Species Recovery. Bioscience. Volume 52. No. 2. February 2002.

The Scope of the Plastic Shopping Bag Problem

How big of a problem do plastic shopping bags pose to the environment?

Since the elected supervisors of Los Angeles' City Council recently voted to ban plastic shopping bags at the city's retailers, largely in response to "clean-water" advocates, who argue that the bags "pollute the ocean and the city's waterways", we thought we'd get a sense of just how big that problem really is.

Our chart below presents the answer, which refers to data that those who support bans on plastic shopping bags frequently cite in advancing their agenda:

The values shown in the chart above were originally reported in 2004. There are a number of points to note about the results for the first-ever worldwide cleanup of the coastal areas of the United States and 100 other countries:

1. The use of plastic shopping bags really began taking off worldwide in the 1980s.


2. By 2003, "environmental groups" estimate that anywhere from 500 billion to 1 trillion plastic shopping bags were being used annually.


3. Despite never having been done before, meaning that about as many bags as could be found would be found during the Ocean Conservancy's one-day long campaign to clean up the world's coastal areas in September 2003, just 354,000 bags were collected. Most, but not all, were made of plastic.

More fascinating to us however, we've discovered that so-called "green" advocates are incredibly fond of recycling the Ocean Conservancy's 354,000 bag cleanup figure from September 2003, citing it as being a valid figure that applies year, after year, after year. We're nearly at the decade anniversary and apparently, only 354,000 bags ever get cleaned up from the world's coastal areas each year!

Either that means the problem is not getting any worse despite a great deal of economic and population growth worldwide in the intervening years, which would have greatly increased the world's consumption of plastic shopping bags, or that these environmental activists just don't care enough about the environment to bother with picking up more than 354,000 mostly plastic bags from the world's coastal areas in any given year.

The alternative possibility is that a large number of environmental activists recycle the data because updating it would take actual effort on their part. Plus, there's the little matter of how foolish they might look if they ever fail to collect at least as many as their apparent annual quota of 354,000 bags!

If only these people cared more about the environment!...

Data Reference

Lowy, Joan. Plastic left holding the bag as environmental plague. Scripps Howard News Service. Seattle Post-Intelligencer. 20 July 2004.

Previously on Political Calculations

• Paper, Plastic or Cloth: Which Bag Is Best for the Environment?

Paper, Plastic or Cloth: Which Bag is Best for the Environment?

Which is the most earth-friendly: paper bags, plastic bags or cloth bags?

The answer to the question depends upon whether or not you really believe in science, because as they say in certain environmental activist circles, the "science is settled"! Here's the summary description of the bag found to be the best for the environment, which is defined as being the bag with the least negative impact upon the environment, as found in a very recent and thorough study on the topic:

The conventional HDPE bag had the lowest environmental impacts of the lightweight bags in eight of the nine impact categories. The bag performed well because it was the lightest bag considered. The lifecycle impact of the bag was dictated by raw material extraction and bag production, with the use of Chinese grid electricity significantly affecting the acidification and ecotoxicity of the bag.

Yes, the convential High-Density Polyethylene (HDPE) (aka "plastic") bag had the least impact upon the environment of all the bags considered in the study, which considered a number of bags made from different plastics, as well as both paper and cotton-based materials!

But that's only considering using each type of bag just once. For many eco-oriented people, the whole point is to reuse other kinds of bags to counteract the perceived environmental hazards posed by the conventional plastic bag.

Fortunately, the study revealed how many times the alternatives to the conventional plastic bag would have to be reused to overcome their own negative impacts to the environment:

Here, we find that if a consumer only uses a conventional HDPE plastic bag just once (say to carry their groceries home before throwing the bag away), a paper bag would have to be reused 3 times, a heavy-duty plastic bag made from Low-Density Polyethylene (LDPE) would have to be used 4 times, a plastic "bag-for-life" made of non-woven Polypropylene (PP) would have to be used 11 times, and a cotton (or canvas) bag would need to be re-used 131 times!

The study reports that a canvas bag is expected to last for 52 trips (Table A.3.1). With that as a reference, a cotton/cloth canvas bag user does over twice the damage to the environment that a plastic bag using grocery shopper who throws away every plastic bag they get immediately after each shopping trip, as they will likely have to replace their more environmentally-destructive bag at least once long before they reach 131 uses!

However, if a consumer reuses 100% of their conventional HDPE plastic bags (say as trash bags), the number of uses needed for the other bags to have a lesser environmental impact than the conventional HDPE plastic bag rises by a factor of anywhere from 2.2 to 2.5, which we see in the table above. For example, that re-usable canvas bag would need to be used at least 327 times to be less damaging to the environment!

Which makes the eco-friendly canvas bag user over six times as destructive to the environment as the conventional consumer who simply re-uses all the plastic bags they get from the grocery store just once.

If only those anti-plastic bag advocates cared more about the environment....

Reference

Edwards, Chris and Fry, Jonna Meyhoff. Life Cycle Assessment of Supermarket Carrier Bags. Report SC030148. Environment Agency.