The Colorado River: Consequences of Hydrologic and Land Use Change

For the past few weeks National Geographic has been publishing a series on the Colorado River Delta (link below), with posts written by Sandra Postel, a writer and consultant on international water issues.

The series discusses a perfect example of anthropogenic changes to both the land and the water cycle. Our book (Principles of Terrestrial Ecosystem Ecology) tells us that “land use changes alter the hydrologic cycle by altering (1) the quantity of energy absorbed, (2) the pathway of energy loss, and (3) the moisture content and temperature of the atmosphere,” and that “lands under irrigation have increased fivefold during the twentieth century.”

This series focuses specifically on the changes that have occurred around the Colorado River, and the consequences to its flow. A particular post entitled “Returning the Colorado River to the Sea” describes the river as one that once teemed with life, and spanned some two million acres, creating one of the planet’s greatest desert deltas. Over half a century of damming and diverting the river’s flow, however, has depleted the river and dried out the delta’s wetlands, such that today it no longer reaches the sea. These are drastic changes to the mighty river that over millenia carved out the majestic Grand Canyon.

The video from the link above does a great job of visually showing the path of the river, the cities and fields that depend on it, and its delta which is completely dry. The good news is that efforts are being made to restore some of the river’s flow, via a binational agreement between the U.S. and Mexico. Over a trial period of five years, the two countries, and the Delta Water Trust together will return one percent of the Colorado’s historic flow to the river and its Delta. If successful, the period will be renewed with the potential for increases in water flow.

Conservationists believe that wildlife will quickly return to delta once water is reintroduced. They have good reason to, after observing a nearby area which in past decades was flooded with water that had been drained upstream for farmland, and which today is teeming with biodiversity.

This seems like a great opportunity to begin to restore a system that has been greatly altered by human action, allowing the river to reach its natural destination – the Ocean.

UVM Student Research Conference

I wanted to use this week’s blog post to share a draft of a poster that my colleague and I will be presenting next week at the UVM Student Research Conference. The contents are particularly heavy on the ecological side of our project, which crucially gathers information that will feed the more socio-economic  portion, via economic models and decision support tools for forest managers. Please feel free to critique and make suggestions. We welcome your input. And be sure to stop by to learn about what other UVM students are working on! (details here)

Forest Ecosystem Service Trade-offs of Salvage Logging Following Wind Disturbance in Vermont Forests

Sarah Pears ( and Eduardo Rodriguez (, Ph.D. students
Kimberly Wallin(, Research Assistant Professor, and Jon Erickson (, Professor


A December 2010 windstorm rushed into Chittenden County, Vermont from the southwest, causing severe damage to patches of trees as large as 50 acres. Windstorms are important disturbances in the Northern Forest, where standreplacing events (e.g. forest fire, insect outbreak) are rare. Resulting damage may include heavy mature tree mortality, canopy disruption, reductions in tree density and size structure, and changes in environmental conditions (Dale et al. 2001). These types of storms are expected to increase in frequency due to climate change (Schelhaas et al. 2003).

After the 2010 storm, forest managers chose various strategies for management, driven by landowner stewardship objectives. Salvage-harvest, the cutting, collection, and removal of trees from damaged forest stands, occurred to varying degrees across Chittenden County. While the outcomes of salvage harvest post-fire have been studied, salvage harvest results and impacts following windstorms have not been adequately documented (Lindenmayer et al. 2008).


The purpose of this study is to quantify differences in terms of forest recovery, carbon sequestration and biodiversity across a range of blowdown and salvage harvest conditions. The study also provides an opportunity to study the spatial variation of these attributes across microsite characteristics including aspect, distance from undisturbed canopy edge, and slope.

Expected Outcomes

Using the results from this proposed study, we will construct and parameterize a model that relates forest ecology and socio-economic impacts to disturbance and salvage harvest in the Northern Forest.
In addition to peer-reviewed scientific journal articles, we will make the study results an recommendations for post-disturbance management available to the community of forest landowners and managers through popular press articles and workshops.


We will study 30 forest sites of various sizes and damage intensities within Chittenden County, VT. Site characteristics: We will measure uncontrolled variation in site conditions,
• Stand age and silvicultural history
• Blowdown intensity and area
• Salvage harvest intensity, area, timing and equipment
• Site location

Forest recovery: We will exhaustively survey standing, live trees within each
site, and compare results with indicators of pre-storm forest conditions
(stumps, aerial photos, forest inventories) to quantify
• Compositional change: percent mortality post-blowdown and salvage
harvest, overall and by species
• Structural damage: change in basal area overall and by species
• Mode of recovery: regrowth, recruitment, release, repression (Everham and
Brokaw 1996)

Carbon sequestration: The Intergovernmental Panel on Climate Change
classifies carbon sequestered by forests in to five pools: above-ground
biomass, below-ground biomass, coarse woody debris, soil carbon, and wood
products. We will measure above-ground biomass (kg/ha) and coarse woody
debris carbon storage (kg/ha) at all sites.

Biodiversity: Ground-dwelling invertebrate community diversity is a generally
accepted indicator of overall biodiversity.
• Ground-dwelling invertebrate community sampling, using pitfall traps and
litter sorting
• Herbaceous plant surveys at sub-plots within sites

Statistics: The study is designed as a hierarchical regression model to test for
the impacts of blowdown damage and salvage harvest across sites. We will
describe patterns within site using a spatially repeated measures model.

References Cited

Dale, V.J., L.A. Joyce, S. McNulty, R.P. Neilson, M.P. Ayers, M.D. Flanningan, P.J. Handson, L.C. Ireland, A.E. Lugo, C.J. Peterson, D. Simberloff, F.J. Swanson, B.J. Stocks, and B.M. Wotton. 2001. Climate change and forest disturbances. BioScience 51:723-734.
Everham, III, E.M. and N.V.L. Brokaw. 1996. Forest Damage and Recovery from Catastrophic Wind. Botany Review 62: 113-185.
Lindenmayer, D.B., P.J. Burton, and J.F. Franklin. 2008. Salvage Logging and its Ecological Consequences. Island Press; Washington, D.C.
Schelhaas, M.J., Nabuurs, G.J., and A. Schuck. 2003. Natural disturbances in the European forests in the 19th and 20th centuries. Global Change Biology 9: 1620–1633.
This project is funded by a grant from the USDA McIntire-Stennis Forest Research Program.

2012 Drought: Fluke or Fate?

The National Oceanic and Atmospheric Administration recently published a report, led by Martin Hoerling, which assesses the origins of the 2012 drought that ravaged the central great plains of the United States. The report describes the morphology of the drought, placing it in historical context, and providing a diagnosis of its causes. It concludes that the May-August 2012 drought resulted mostly from natural variations in weather, with neither ocean states, nor human-induced climate change having played significant roles in the rainfall deficits.

Understanding the cause of the drought is important, as NOAA itself describes it as the worst to afflict the country since 1956. This is based off of the Palmer Drought Index, which estimated that 55 percent of the contiguous United States was in moderate to extreme drought last year, versus 58 percent in the 1956 drought (Reuters). The NOAA report further states that “precipitation deficits for the period of May through August 2012 were the most severe since official measurements began in 1985, eclipsing the driest summers of 1934 and 1936 that occurred during the height of the Dust Bowl.” (NOAA)

Media outlets were quick to jump on the NOAA report. As I write this blog post, CNN’s most popular story, as measured by its NewsPulse tool, is entitled “Study: Last year’s drought not human-induced.” Yesterday, Huffington Post and Climate Central both published similar articles: “Climate Change-Drought Connection Not ‘Significant’ In 2012 U.S. Dry Spell, NOAA Reports,” and “Global Warming Not Significant in 2012 Drought: Report,” respectively.

As expected, many do not agree with NOAA’s conclusions, and Dr. Kevin Trenberth of the National Center for Atmospheric Research has led the charge to criticize the report. He describes it as “needlessly confusing” and “scientifically problematic,” and warns that it is already leading to misleading headlines (presumably referring to a few of the above).

Trenberth states that the report asks the wrong questions, and then does not provide useful answers to the questions being asked. He also attacks it as being incomplete, arguing that the study failed to “say anything about the observed soil moisture conditions, snow cover, and snow pack during the winter prior to the event in spite of the fact that snow pack was at record low levels in the winter and spring” and “no attempt was made to include soil moisture, snow cover anomalies, or vegetation health” in the climate model runs performed (ThinkProgress). He concludes that “just because Hoerling couldn’t replicate the drought with his computer simulations, it doesn’t mean climate change had nothing to do with the 2012 Central Great Plains Drought — let alone the entire 2012 drought and the current 2013 drought.”

Further criticism of the report points to the narrow window of time to which the study constrains the drought. While it focuses on the summer months between May and August, data indicates that the drought is ongoing. The video below, posted on the report’s main page, seems to support this, as it shows drought affected areas between November 2011 and December 2012.

The debate is a reminder of the complexity our natural systems, and the phenomena that shape and change them. As we work on our models for our final projects, we may end up being daunted by the difficulties of trying to simulate nature. This is why it’s important to keep the big picture in mind. What are we trying to describe? Why is it important? What do we need to describe it? And what do we incorporate, knowing that models are inherently imperfect, and given that we have data, time, and resource constraints that limit our possibilities?

Salvage logging following wind disturbances

My main project is related to severe windstorms, and the ensuing salvage logging that is frequently practiced by forest landowners, with a specific focus on parcels of land within Chittenden County in Vermont. Though wind disturbances that cause substantial damage to trees have been historically infrequent in the Northern Forest, climate change models predict an increase in the frequency and intensity of storms for this region in the coming decades.  When severe wind damage does occur, forest managers often have strong incentives to perform varying degrees of salvage harvest, creating a second disturbance. To date, the literature has not adequately described the effects of wind storms on forests.  And the ecological and economic consequences of salvage harvest post windstorm are also not well understood. However, a severe storm that occurred in December of 2010, leading to vast areas of wind damaged trees, is an opportunity to improve our understanding of these issues. The goal of my research is twofold: 1) Describe the effects of salvage harvesting on ecosystem services provided by the Northern Forest, with a particular focus on the tradeoffs between the provisioning of timber resources, and regulating and cultural services such as carbon sequestration, soil formation, and recreational opportunities; 2) Use these data and incorporate them into the decision making process of landowners, so that they have more information when deciding whether or not to harvest, and how much to harvest.

This class has encouraged me to think of the spatial aspects that could go into the project. There are two ways in which I envision spatial analysis being useful in this research.

The first requirement is simply to make our study sites spatially explicit, by establishing their physical boundaries on a map. Once we add other layers describing the physical characteristics of the surrounding land, we can then get a better understanding of the terrain. Layers describing the slope and elevation of the land would be useful, for example, since they are likely to influence the cost of performing salvage logging. A layer showing nearby roads would allow us to calculate their distance from our sites, which would also influence costs. A third potential factor has to do with aesthetics. A landowner that uses his land for recreational purposes might not be as willing to harvest damaged trees, since the barren land would be detrimental to their income. It may be tricky to estimate the penalty they would suffer from harvesting, but certain criteria could be established based on physical land characteristics to assist in producing such an estimate. The idea would then be to apply a set of rules that tie specific land characteristics to increased costs of salvage logging.

If this idea were successful, there is potential for further implementation. Since climate models predict more storms that are more intense in the coming years, we could create scenarios that simulate the one that occurred in 2010. An interesting goal would be trying to access the areas that are more prone to wind damage in a given region, and then analyzing the effects of different levels of storm intensity in those areas. Using the parameters established in the previous paragraph, we would then already have a methodology set up to perform a cost/benefit analysis of salvage logging in the areas affected in the simulation.

Flow Chart


The flow chart above generally outlines the major steps that would be necessary for this project. The study area of each individual study site would need to be defined in step 1. In the next step, all of the layers with data relevant to the study would be collected, and combined into an overlay for the third step. In step 4, specific formulas and calculations would be required to obtain the total cost the particular land characteristics would incur in terms of performing salvage log operations. And finally in step 5, different harvest intensities could be evaluated, and compared to the economic benefits that the landowner would obtain from salvage logging, allowing them to make an informed decision. Further steps could be added if the previous steps were used to engage in climate change scenario simulations.

Lake-effect Spring Break

I was able to briefly escape Burlington during spring break for a few days. Though I didn’t venture far enough to enjoy real spring weather, I did get to witness an interesting weather phenomenon: lake effect snow.

I woke up on Friday morning to beautiful weather here in Burlington: clear blue skies, and temperatures above 40 degrees. In Hamilton  NY, however, which was my destination for that day, they were getting between six and 10 inches of snow. Looking at the map below, we get a few hints as to why this would happen in regions that are relatively close to each other.

Hamilton and Burlington are located at latitudes of 42.8 and 44.5 degrees, respectively. In fact, most of the United States falls within latitudes of 30 and 60 degrees. And as you might recall from question 26 of the exam, and from the figure below, this means that the Westerlies are the prevailing winds in the US.


Combining the Westerlies with two major land-forms seen in the first map, the Great Lakes and the Adirondack Mountains, it becomes clear why Hamilton was getting so much snow while Burlington had perfectly blue skies.

The figure below does a great job of explaining the lake effect. The westerlies blow cold air over the comparatively warm waters the Great Lakes, gathering and retaining moisture, until the saturated clouds hit land. In this case New York State, which lies east of Lake Ontario and Lake Erie, gets hit with lake effect snow.

Lake Effect Snow

Eventually this saturated air reaches the  Adirondack Mountain, which blocks the moist air. The humidity stays on the western side of the mountains, while on the eastern side, the air is dry and the skies are clear.

The map below shows areas prone to lake-effect snow. Notice the how most of New York State is engulfed, whereas Vermont is left out, due to the protection of the Adirondacks.


I left Burlington in the afternoon, and interestingly enough, by the time I arrived in Hamilton that Friday, most of the snow had already melted and the sky was also clear! Apparently the whole system went through in a few hours, and a warm air mass moved in right behind the snow storm.

Midterm Questions

1. Describe the three major cells of vertical atmospheric circulation. Feel free to use a diagram.


Hadley, Ferrell, and polar cells are the three major cells of vertical atmospheric circulation. Air warms and rises at the equator due to intense heating. After reaching the tropopause, the equatorial air moves poleward to about 30° N and S latitudes, where it descends and either returns to the equator, forming the Hadley cell, or moves poleward. Cold dense air at the poles subsides and moves toward the equator until it encounters polewardmoving air at about 60° latitude. There the air rises and moves either poleward to replace air that has subsided at the poles (the polar cell) or moves toward the equator to form the Ferrell cell.

2. What are disturbances? Give at least five examples.

A disturbance is a relatively discrete event in time and space that alters the structure of populations, communities, and ecosystems and causes changes in resource availability or the physical environment. Examples are: insect outbreaks,, fires, hurricanes, floods, glacial advances, volcanic eruptions.

3. Explain solar radiation budgets and how changes in albedo may affect them.

The solar radiation budget refers to the balance between incoming and outgoing short-wave and long-wave radiation on a particular surface, be it a plant leaf or the entire globe. Albedo refers to the shortwave reflectance of the ecosystem surface. An example of a low albedo (low reflectivity) natural surface is the ocean (0.03-0.10). Fresh snow is an example of a high albedo surface (0.75-0.95).

Biodiversity: A Boon or a Burden for Human Well-being?

I’m often really impressed that incredibly lengthy and detailed documents such as the Millennium Ecosystem Assessment (MA) actually end up as an organized final product. The amount of people, time, and data that must be managed in order to produce these reports is astounding, and the process of compiling everything into a coherent text must be a logistical nightmare. Nonetheless, they exist, and several versions of these reports exist and can be found online (

In this post I’ll specifically refer to the Biodiversity Synthesis, which aims to summarize the findings from the MA assessments on biodiversity and human well-being. This objective, in and of itself, has been a source of debate (Reyers 2012). When discussing the importance of biodiversity, the report states that “biodiversity is essential for ecosystem services and hence for human well-being,” (pg. 30). There are those who view this anthropocentric end-goal of enhancing human well-being, through the mechanism of preserving biodiversity, as a wrong-headed approach, since there is an inherent value in biological diversity, regardless of whether it benefits human beings (McCauley 2006 & replies). The argument is that conserving biodiversity should actually be the end-goal, and that focusing on the services that benefit humans misdirects conservation efforts. No matter which side of which side of the argument you align yourself with, the MA Biodiversity Synthesis has plenty of interesting material to discuss.

The two “key messages” (pg. vi) that most captured my attention were related to the speed of changes in biodiversity, which in the past 50 years have been more rapid than at any time in human history, and to the trade-offs that exist between achieving the 2015 targets of the Millennium Development Goals and the 2010 target of reducing the rate of biodiversity.

The chart below demonstrates the extent to which species extinction rates have increased in the distant past compared to the recent past, and what this exponential trend would mean if extrapolated into the future.


Yet the difficulty of curbing this disturbing trend is all the more complicated when efforts to mitigate species loss directly conflict with goals to promote human development. It is therefore important to keep in mind that since “biodiversity underpins the provision of ecosystem services that are vital to human well-being, long-term sustainable achievement of the Millennium Development Goals requires that biodiversity loss is reduced” (pg. 80). In other words, while there are are contrasts between the MDG and biodiversity conservation, it is imperative that we also acknowledge the long-term relationship that exists between the two. Narrow, short term-thinking is likely to be harmful to both goals.

As cumbersome as it might be to produce them, reports of this nature are undoubtedly full of useful data. I have used them as sources in projects before, and anticipate that I will continue to do so in the future. However, they mostly represent only a snapshot of past and current state of affairs. Though they might predict future trends and even recommend policy, it is important that as time goes by, new data be incorporated into updated versions in order for the documents to remain relevant, and useful to decision makers.