Sunday, February 24, 2013

How many acres of forest lost in PA due to Marcellus wells? How many trees?

(4-19-14) Please see the UPDATE below.

Link to this:

Someone asked me to estimate (ballpark) how many trees have been lost in NY due to pipelines.

Yet, in NY there are many pipelines, and many of them are decades old.
So this number is very hard to estimate, and requires assumptions about time horizon,
width of rights of way for pipelines of various sizes. Also, getting the raw data is difficult.

It's actually easier to ask:
"How many trees have been lost in PA due to Marcellus exploration?

I like doing these kinds of guesstimates, so I gave it a crack....

It's pretty staggering:
Here is the calculation. This numerical analysis is based on scientific data in published sources, so my answer is probably "close", within an order of magnitude of being correct.

How much forest is lost due to each well pad?

``A recent analysis of Marcellus well permit locations in Pennsylvania found that well pads and associated infrastructure (roads, water impoundments, and pipelines) required nearly 3.6 hectares (9 acres) per well pad with an additional 8.5 hectares (21 acres) of indirect edge effects (Johnson, 2010).``  --

This is the reference:

Johnson, Nels, 2010, Pennsylvania energy impacts assessment, Report 1: Marcellus Shale Natural Gas and Wind, The Nature Conservancy, Pennsylvania Chapter, and Pennsylvania Audubon, accessed January 12, 2011, at:

We'll use the conservative number of 9 acres per well pad.

How many Trees per acre in PA? (approximately)

250 @ 2"
100 @ 4"
50 @ 6"
40 @ 8"
25 @ 10"
20 @ 12"
14 @ 14"
10 @ 16"
~500 trees per acre of forested land (of various sizes.)

Same document says: "Pennsylvania has 16,652,100 acres of forest land". 
Wikipedia says PA area is 46,000 sq mi., which is 29.5 million acres. 

This means 57% of PA is forested.

How many wells per pad?

``While multi-well pads have increased over the past five years, the overall ratio of wells-per-pad remains low. Since 2006, over 1,553 Marcellus well pads have been developed to support 3,279 Marcellus wells in Pennsylvania indicating a well-to-pad average of 2.11. The data show that this ratio is increasing: in 2009 the average was 1.53 wells per pad, and in 2010 the average was 2.15. ``


So let's use 2 wells per pad for our estimate.

How many wells drilled in PA so far?
John Holko says it's 3700:

Tony Ingraffea says it’s 5,500:
Some disagreement may be due to the ambiguity of “wells drilled”.
Are we talking about vertical wells? or the horizontal legs?
We want to be conservative, so let’s use 3,700.
How much of PA is farmland?

OK, now we have everything we need. Let's run the calculation:
1: Number of wells so far / number of wells per pad = number of well pads.
  3,700 / ~2 = 1850 well pads in PA

2: Number of well pads * acres disturbed per well pad = number of acres permanently lost
1850 * 9 acres  = 16,650 acres lost forever (*).  

16,650 * .57 (57% forested PA avg) = ~9,500 acres of PA forest lost forever. 

Multiply this times 2.3 to include edge effects = ~22,000 acres 

16,650 * .27 (27% PA is farmland) = ~5,500 acres of PA farmland lost forever. (this may be greater due to a segmentation effect similar to forest edge-effects)

3: Number of acres lost * number of trees per acre = number of trees lost (forever)
9,500 * 500 = 4,750,000 trees lost, forever.(*) 

Multiply this times 2.3 to include edge effects = ~11 million trees.

(* = since the access roads, well pads, pipelines, etc. are permanent rights-of-way.)

So there's your answer.

So far, Pennsylvania has lost ~5 million trees, over 16 thousand acres of forest, lost forever due to drilling. (These are conservative estimates).

(Question for you to ponder for extra credit:
How much other life WAS supported by those 5 million trees?)


I do not believe this includes new large transmission lines such as the Constitution,
which is 121 miles * 50' permanent easement. (about double is needed during construction)

121 mi * 5280 ft/mi * 100' construction easement = 64,888,000 ft sq. = ~1,466 acres = ~1,100 football fields.

How many trees destroyed for the pipeline?

1,466 acres total for the pipeline R.O.W. * 500 trees per acre *.57 (percent forest) 
~430,000 trees.

How much farmland is destroyed for the pipeline?
1466 acres * .27 (27% farmland) = 400 acres farmland destroyed (~300 football fields)

They say that half that will be "reclaimed".
Over how much time...? 20 years? 50 years? 

Will it ever be the same?

Final thoughts (in case the above is not enough to give you nightmares):

Tony Ingraffea says PA is only 2% developed. So to see what PA will look like, multiply the above numbers by 50.

From Robert Boyle:
Add in this factor: One acre of northern hardwood forest sequesters 100 tons of CO2.  Cheers.


UPDATE: 4-19-14

I first did this calculation a year ago. Stateimpact says the total number of active shale wells no in PA is 6,391. So my numbers above are low by 1.73x.

Here are the better adjusted numbers:

16,409 acres in PA have been destroyed so far.(25.6 sq. miles)
38,000 acres if you include edge effects.
9,515 acres of farmland gone forever.

If we assume 500 trees per acre, this means over 8 million trees have been destroyed in just about 7 years for gas drilling / shale gas fracking in Pennsylvania.

A new report from the PA DCNR says that of state-managed forest land, the total number of lost acres is 1,486. This may be true, but the total number of lost forest in PA including private lands is 11x this number.

May you, and all beings
be happy and free from suffering :)
-- ancient Buddhist Prayer (Metta)

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