Jun 1, 2010 0
BOTE stands for Back-Of-The-Envelope and is a common phrase applied to macroscale or overly coarse calculations done kinda haphazardly. Well given this caveat I came across an article from The Telegraph (UK) titled “Detroit to Bulldoze Thousands of Homes in Fight for Survival”, which quoted the following statistic:
“Almost a third of the city’s 139 square miles is vacant or derelict, though its land area would comfortably fit Manhattan, San Francisco and Boston, cities with combined populations of three million.”
I thought it would interesting to apply some of my dissertation data to figuring out how much of Detroit’s CO2 footprint could potentially be offset if this land was reforested. So, here it goes step by step.
(33%*139 Sq Miles)=45.87 Sq Miles of vacant or derelict land
Convert to Hectares=45.87*259>11,880 Hectares
Hectares to Square Meters=11,880*10,000>118,803,229 Square Meters
Grams of Carbon per Square Meter Per Year (From my Thesis work we assume the average for Great Lakes forests is 10,849 g C m-2 yr-1)=118803229 Square Meters*10,849 g C yr-1>1,288,896,240,464 g C m-2 yr-1
Metric Tons Per Year=1,288,896,240,464 g C m-2 yr-1*0.000001>1,288,896 Metric Tons of C captured Per Year IF the 45.87 Sq Miles of vacant or derelict land was reforested!
NOW lets put this number in perspective relative to Detroit’s actual emissions.
If we assume Detroit’s population (For Now!) is 951,270 and residents of the city emit approximately 23.4 Tons of CO2 per person per year that comes out to 22,260,764.4 Tons of CO2 per year for the city of Detroit, which means……..
The figure calculated above for potential carbon captured by reforestation of vacant and derelict land (i.e., 1,288,896 Tons of CO2 per year) equals 5.80% of total city-wide emissions. This number while not jaw dropping is far from trivial and any efforts to implement such plans should be encouraged locally and nationally as 5.8% of anything at that scale adds up and would greatly increase the quality of life in Detroit. Similar projects are sprouting up in neighboring F lint, Michigan as well as places as far off as Chilibre, Panama. Likewise we have data on those areas as well and could do similar BOTEs in an effort to quantify the impact of reforestation, both above- and belowground.
We have an interesting love affair with shopping in this country and I thought it would be illustrative to quantify its influence on our land to capture carbon. First lets quickly look at how much we love shopping and how much our economy (and by association China, Japan, the EU, etc etc) depend on our insatiable appetite for stuff. It is true that we have come down off our Great Depression high of 83% Consumption as a percent of GDP, but for the better part of the last 63 years we have maintained a relatively static 65% of GDP attributable to consumption.
However, this figure has risen substantially in the last 20 years from 62% in 1981 to 70.8% in 2009.
You might say well what does my local strip mall have to do with CO2? Well your local strip mall displaced some sort of native ecosystem that, up until the big trucks and earth-moving equipment came, was drawing down CO2 via photosynthesis and decomposition of biomass to produce soil carbon.
Well that has had a cumulative effect and I have attached a couple of graphs to demonstrate this phenomenon. Using Gross Leasable Area (GLA in sq feet) per person data back to 1990 we can calculate above- and belowground carbon displacement via shopping center expansion (Blue Line), which sums to about 218 Million Metric Tons between 1990 and 2009, which when subtracted from Total US CO2 Emissions gives us the inset in the figure below.
How you might ask does this relate in-terms of percentages? Well it turns out it is quite similar in magnitude to what I described for Detroit. If we assume - based on EIA assumptions - that Residential emissions is 6.65% of the story here in the US with respect to CO2 emissions than the above removal of native ecosystems for shopping centers translates to anywhere from 2.78 to 3.31% of Residential CO2 emissions across the entire US. However, if we had implemented the type of plain they are considering in Detroit across all fifty states beginning in 2005 we would have had the opportunity to “offset” 3.13% of our emissions per year as opposed to 2.85% between 1990 and 2004. You may say what is the big deal about 2.85 to 3.13%? Well when you consider we are measuring our fiscal and monetary peril here in the US with values like 3 to 12% of GDP and the fact that US GDP is expected to grow by 3.0% in 2010 v. 0.18, a decline of 1.83, and 2.53% in 2009, 2008, and 2007, respectively…Then the numbers I present here start to take on a whole new meaning. The harm inflicted by shopping centers - never mind the removal of capital and liquidity from local markets via large multinationals like Wal-Mart and Best Buy - is not just skin or in this case soil surface deep. It impacts the ability of communities and watersheds to withstand flooding, retain nutrients that would otherwise pollute reservoirs and aquifers, moderate temperature and moisture volatility, and propagate a sense of ownership among residents. The data back it up. Chalk another one up for BOTEs!