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Homework assignment #2
Below are 5 pages taken from the 2012 ECOLOG‐L listserve for ecological discussions. It concerns a
question asked to the group by Dr. Stephen R. Johnson about carbon sequestration.
Please do the following:
1. Summarize the debate, indicating what position each person responding is taking in the
debate and summarizing their points.
2. Indicate which points you agree with and don’t agree with and why or why not.
3. Your written summary should be 1‐2 pages.
Dear Ecolog‐ers,
I am designing a tree planting project designed to counter CO2 production at a college in south central
Iowa. Students will be involved in planting. I have heard that the Tulip tree (Liriodendron tulipifera) and
Sweetgum (Liquidambar styraciflua) are both good candidates for carbon sequestration and I wonder if
there is any primary literature that backs the claim. Also, are there any other tree species with high
rates of carbon uptake and biomass accumulation, fast growing and long‐lived and with low
maintenance and perhaps with any or all of these properties reflected in any scientific studies.
Dr. Stephen R. Johnson
Your criteria are shared by countless homeowners wanting to landscape their yards (fast growing, longlived,
low maintenance). Unfortunately, there are physiological tradeoffs involved, whereby fast growing
trees tend to “live fast” in other ways, too, and hence are as a general rule not long‐lived. Think about
the way forest succession works: fast growing trees fill in gaps quickly, reproducing before the
competition catches up; slow growing trees are the shade tolerant ones, coming up underneath the fast
growing pioneers and eventually supplanting them.
From what I have read of carbon sequestration (as it is not my primary area of knowledge), old‐growth
forests hold a lot of carbon, but do not take it up quickly; the decomposition of old trees and the carbon
uptake of growing trees about cancel out, making the old‐growth forest approximately carbon‐neutral.
Young forests take up carbon quickly, but as they age, the uptake rate slows down. When a tree
decomposes, all the carbon sequestered in its biomass is re‐released. So to have effective sequestration,
you would have to have a steady supply of young trees taking up carbon, without a concurrent stream of
decomposing trees. Net growth would have to exceed net decomposition. In other words, the only
long‐term way to counteract ever‐increasing CO2 emissions, is to have ever‐increasing acreage of forest.
Jason Hernandez
I’d like to supplement some of the points made by Jason Hernandez, which are all right on.
The best way to promote carbon sequestration is to plant a resilient forest: one that has a combination
of tree species so you are buffered against pests and diseases, and then plan for what you will do with
the trees after they die. If you plant trees which can be used to create furniture, such as cherry, oaks or
pines, you will be creating a more permanent carbon sink. Also you can direct dead trees to a facility
which will burn them for fuel: this will not only produce “carbon neutral” power, but will prevent more
fossil fuels from being used. Finally, you can compost tree matter (leaves, pruned branches, etc).
Although much of the carbon will be released, some will remain in the soil, which is actually a very
under‐appreciated “carbon sink”.
An aside: besides providing for carbon storage, trees help cities in a huge variety of ways. They improve
urban streams by intercepting storm water (prevent flooding), stabilizing and creating soil, contributing
organic matter, and cooling stream water. Trees cool streets and buildings, reducing air conditioning
costs (and therefor lessening the electricity needed to climate control the building). They remove
pollutants from the air, and provide habitats for birds, bugs, squirrels, and other wildlife.
Katie Rose
I share Rose’s comment about the Hernandez post, which I agree is “right on.”
I am not opposed to Rose’s comments, but they do strike some complex chords for me.
Rose is right on when she mentions resilience, and I would add that not only diversity in species is
important, but diversity of age classes and genetic variation also is important‐‐yes, more important than
species diversity in some contexts. One thing troubles me a bit however. Well, maybe it troubles me a
lot.
The implication of Rose’s and Johnson’s remarks seems to be that one can decide to plant all kinds of
different species without regard to the suitability of the site for the species, although they perhaps
believe that such goes without saying. In my days in the U.S. Forest Service, for example, we were
careful, perhaps absurdly so, about the provenance of the seeds collected, taking care to note the
elevation, orientation, slope aspect, etc. so that the resulting saplings could be planted in comparable
circumstances, believing that a good match of the genes to the site would maximize the potential for
survival (e.g., temperature tolerance range, etc.) and result in optimum growth potential. I know that
forest science has undoubtedly come a long way since then, so I look forward to those more advanced
to bring me up to date.
But what disturbs me even more is the unstated possibility that various sorcerers’ apprentices might let
loose designer‐trees based upon some marginal, perhaps largely fictional, increased ability to provide a
single “ecosystem service.” (For some reason the Irish potato famine comes to mind . . .)
The request also strikes me as more horticultural than ecological, and Rose and Johnson seem to imply
that planting trees in South‐Central Iowa (or any other location) can be done without regard to
ecological context. While all the things Rose mentions are “good,” and can be part of the ecological
context, I often hear/read/see similar tree “boosterism” overriding ecosystem concerns as wellintentioned
prescriptions without regard to context.
Also (almost?) never mentioned are the supposedly tangential but real factors in the net‐energy and
carbon‐balance equations that include energy consumption and carbon‐release numbers associated
with the production, transportation, and planting of growing trees. I stand ready to be further
enlightened on this subject as well.
Wayne Tyson
Tyson adds a much appreciated nuanced response. I agree that ecological context should be taken into
account whenever possible, as well as with his point about looking at the whole carbon footprint of a
planting project. I am unfamiliar with the ecological context of South‐Central Iowa: I was answering
generally without looking at the specific question. So first generally:
Planting trees which were grown nearby not only lowers the carbon balance of the project (through
reducing transportation costs), but also lowers the chance of pests being spread (which often happens
through the movement of nursery stock). Furthermore, planting trees grown in local nurseries makes it
more likely that the trees are already adjusted to the local climatic conditions. I agree that trees should
be planted in the context of the area: not only will this make their success more likely, but can help
boost populations of native trees.
Both age diversity and genetic variation are an important component of a healthy forest, but may be
difficult to accomplish. Age diversity requires long term planning. In Durham, NC we are currently
experiencing the result of a lack of this planning: the city is filled with beautiful willow oaks, which have
reached their age limit and are now dying more or less all at once. My impression is that within species
genetic diversity is hard to accomplish when utilizing nursery stock. Thoughts?
Now, as to specifically planting trees in South‐Central Iowa: Often we move without looking at the
larger effects on the ecosystem. What happens if the trees planted escape and take over? Are we
planting trees easily controlled, or does it matter? In the Carolinas we have problems with escaped
China Berry and Bradford Pear and are beginning to see the escape of Lacebark Elm. However, in the
face of the dramatic loss of forests across the Midwest due to the beetles, maybe we should be actively
creating forests in other locations. Or should we working to maintain the ecosystems around us how
currently are, remembering that they are as much as a verb as a noun?
Perhaps this is too big of a question for this thread, but I am curious to hear what those with more
experience than I think.
Katie Rose
Rose’s additions and clarifications are illuminating. My concerns too are general‐‐related to principle‐‐
not specific to the South‐Central Iowa area. While I am not overly concerned with individual projects at
local scales, particularly urban areas, I am concerned with the impression left with the public at large,
upon which ecological distinctions are largely lost. And, of course, the implication that tree planting on
a scale actually large enough to have any measurable effect upon global warming can be effective
enough is disturbing, even though I do not necessarily wish to imply that the case instant is itself all that
disturbing.
I only hope that students of all ages and the public at large are not mislead into thinking that the rather
romantic practice of tree planting, whether or not a site is actually suitable or historically a tree or forest
habitat, will even be a preferable allocation of concern and investment in “solving” the global warming
phenomenon. Such investments may be better directed at oceanic organisms and scales, and certainly,
as I believe Hernandez may be suggesting, that simply stopping the wholesale destruction of forests,
particularly in the tropics, are more likely to have an effect on the carbon balance than Arbor Day‐like
projects that, while perhaps consciousness‐raising, simply seduce us with an appealing fantasy rather
than actually educate and move in the direction of actual solutions.
I would emphasize that considering the ecological context is ALWAYS possible; and it’s high time that
horticulturalists realize that they can choose to move from fascinating fantasies toward even more
fascinating realities if they do so. The too‐common, even prevalent idea that landscaping and gardening
as currently practiced is “natural” or yes, even “ecological” is in fact far from ecological or natural is
largely fiction, and fostering that idea is simply fraudulent.
I hope that Johnson, Hernandez, Rose, and similarly enlightened folks will propagate the idea that urban
spaces actually can be made to better fit into local ecosystems, not only without giving up aesthetic
considerations, but actually enhancing them.
The answer to the genetic uniformity issue with nursery stock is to stop using it‐‐at least until the
nursery industry stops its industrial‐production obsession. Throw out the nursery catalogs. Look to the
kinds of ecosystems that existed prior to their destruction, and at least exhaust the ecological options
(of which most of the nursery/gardening/landscaping industry is ignorant of and even biased against)
before resorting to non‐indigenous species‐‐however, when this is done, it may be better, in ecosystem
terms, for the species selected to be aliens from very different climatic and ecological conditions so that
reproduction is prevented. Selecting species that are well‐adapted can seriously backfire, simply
because the selected species came from a similar climate on another continent. Liquidambar, for
example, can be a weedy tree in some locations beyond its natural or original range.
And above all, discard the notion that GMO trees will provide a solution to global warming for the fraud
that it is, promulgated by corporate profiteers, not responsible natural scientists. Any additional
sequestration that some lab‐created and patented tree variety MIGHT (or might not, despite reckless
claims) provide would have to be so miniscule as to have no significant or actual effect upon global
warming.
My purpose in commenting here is to support and supplement the comments of Rose and Hernandez
and to better understand what Johnson is proposing, not to dictate or micromanage from afar. I do not
expect great changes in established habits overnight, but I do believe that ecologists should stand up
and be counted, and help the industries that deal in living things to make better choices. Homo sapiens
has been increasingly deluding itself for the last ten millennia or so, and it’s time we started to make
amends for the damage we have done to the earth in the most sensible way possible. And it IS possible.
It’s just a matter of the knowledge, the understanding, and the will to do so.
Wayne Tyson
To consider the possibility that using nursery stock has very negative ecological consequences one need
only visit a large scale tree and shrub production facility. Certainly the quantity of fertilizers and
pesticides used, coupled with extensive runoff (the largest one in Oklahoma is in the Ozarks east of Tulsa
on steep terrain with very shallow and rocky soils in a karst geology) have potentially devastating
effects.
Cities and other jurisdiction can (and I believe a few have) develop codes that require developers to
leave what is there so far as possible. A smaller total developed footprint can allow native landscapes
(whatever that means) to remain in place. This is not a new notion.
But a lot of the work that is contemplated by cities and developers today is renovation in existing
developed property, some of it having displaced “native” landscape decades ago. My small city has in
place one of the nicer city parks in this area. It was placed atop a former dump (that was there long
before the term or the practice of “landfill” existed). The dumping had simply taken place amongst
clumps of native grasses and trees (for those familiar with the southern plains, it is in the mixed
oak/prairie area known as the “Cross Timbers”). With careful work, the city was able to get a quite nice
semi‐natural park established, and the native trees and meadows that sit atop the hills complement the
playgrounds and picnic areas in riparian areas. Some replanting was done, mostly with locally native
species that are fairly easily established, like Cedar, Elm, and Shumard Oak, rather than the more
difficult cross timbers species such as Post Oak and Blackjack. The hillside and hilltop woods
themselves, however, are native Cross Timbers.
Was carbon sequestering a consideration in the park development? Not at all at the time, several
decades ago. Is it a reasonable factor to consider now for such work? Probably not. Tyson is correct,
that a different attitude and action regarding the large‐scale removal of native ecosystems is needed to
have any effect. But, has the increase in wooded area in the eastern U.S. over the past century slowed
the advance of climate change? I haven’t seen an adequate analysis to know.
McNeely
This sounds like a good example of the integration of landscaping with ecosystem restoration,
management, and preservation that could come to characterize a more sensible, useful, aesthetic, and
more efficient approach to our relationship to the land right under our feet as well as the earth itself.
Indeed, we may never know the effects of small‐scale projects on climate change, but everything has to
start someplace, and if such projects give rise to greater awareness that produces a paradigm shift
within individuals and cultures, then the implications are for enhanced ecosystem health on a large
enough scale to have effects on many aspects of global systems.
Wayne Tyson
This thread often employs ‘natural’ and ‘ecological’ as proxies for ‘good’ or ‘proper’ or ‘appropriate’ or
‘desirable’. Using some past condition to exemplify a desired future is commonplace, but that past is
always poorly documented and most of our ‘knowledge’ of past conditions is selectively conjectural or
inferred. That is the standard recipe for nostalgic yearning.
It is also clear that ‘sequestering’ carbon as biomass does not override concerns the commenters have
about belonging, structure and longevity, also invoked ‐‐ again vaguely ‐‐ as proxies for ‘good’ or ‘proper’
or ‘appropriate’ or ‘desirable’.
It remains arguable whether ecological communities are much more than an instantaneous reflection of
the contingencies of the story of life on earth so far. That story from here on out will likewise entail
whatever happens next. But apply any metaphor you like (restoration, turning the clock back, putting
the toothpaste back into the tube, putting Humpty Dumpty back together again) what happens next is
not going to be a repeat of what happened before, and we can never look forward with clarity or
confidence beyond simple, proximate causes and effects.
To paraphrase a non‐ecologist, life is happening while we make other plans. Meanwhile, ESA’s finest
minds make plans framed primarily by fear and loathing of certain change in uncertain directions. To
paraphrase another non‐ecologist, how’s that workin’ for ya?
Matthew K Chew
