Ecological Perspective

Habitat Corridors: Practical Application

2012-02-03T17:48:00.000-08:00

Here's a pretty fitting follow-up article to the entry I posted about habitat corridors. This article discusses a design for creating habitat corridors over highways. This isn't an entirely new concept, but the modular design of the bridge is very creative and interesting.

As discussed in this article and the earlier blog entry, habitat corridors are needed to connect otherwise isolated patches of habitat. In this particular situation, it was necessary to find a safe way for organisms to cross a highway that runs through a national park (safe for both the organisms and motorists). A design company created a habitat bridge with some very cool specialized features. First of all, the bridge was constructed in such a way that if the the highway ever needs to be widened, the bridge could easily be adjusted to handle the expansion. This is a great example of realistic foresight in ecological design. By recognizing simple truths in our society, the designers were able to create a solution with a much greater design life by making it adaptable.

Continuing this spirit of adaptability, the bridge was designed in a modular fashion, meaning that "modules" which contained different types of habitat could fairly easily be installed or removed from the bridge. Once again, this makes the bridge highly adaptable, meaning that it not only could be used in a variety of locations, it could also be altered to mimic any changes in the surrounding environment. This easy adaptability is a very real concern in ecological design, especially when creating a structure that is meant to last for such a long period of time. We are already seeing a shift in habitat zones due to climate change, so creating structures that can change along with the environment greatly increases their value, and the duration for which they could potentially be useful.

The research that was discussed in my earlier blog post could easily be used to help make this bridge as effective as possible by optimizing the type and distribution of habitats on the bridge. It could also be used to try to make the bridge as appealing as possible to the organisms that may use it. It’s important to remember that this is still an unnatural structure, and as such we need to consider exactly how to make it as easy as possible for animals to become accustomed to using it.

Overall, this article does a good job of demonstrating both the creativity that is going on in ecological design, and how academic research can easily be applied to create practical solutions to real-world problems

Thanks for reading,
Adam

Stream Restoration: Focus on Design

2012-01-30T12:43:00.000-08:00

I thought it might be worthwhile to look at the design process that I briefly discussed in the last post, as it's a pretty good example of ecological engineering in practice.

Firstly, it's important to understand exactly why it was deemed necessary to consider ecological concepts in this design. Unfortunately, usually when this type of problem occurs, a solution is created that is driven solely by engineering concepts, with little regard for impacts on the ecosystem. However, this particular project existed at a happy intersection of concerned citizens, rare habitat, and a moderately health (read: salvageable) ecosystem. Perhaps most importantly, at least from an economic standpoint, was the concerned citizens. Many of the homeowners who lived near the stream, and several members of the city government, were nature-lovers. They lived near the stream, or visited it often, because it was not only a nice view, but an interesting area in which to hike and explore. This interest from the citizens was further bolstered by the fact that the stream in question was a rare warm-water stream habitat, one of only a few in the region. Finally, it was important that after conducting both geological and organism population surveys of the area, we were able to determine that this rare and valuable habitat could be restored and saved for a reasonable cost. The union of these three factors led to the citizens and city seeking out an ecologically-minded solution to their problem.

Once it was clear that the health of the ecosystem would be a crucial factor in any designs, I got to work developing a solution that would address all of the stream's issues. After determining that one viable solution would be the installation of constructed riffles, I set about figuring how best to design and implement the riffles. In order to make the design as ideal and efficient as possible, I considered several factors. First, I conducted a survey of existing riffles in healthier parts of the stream. This gave me an idea of the size, slope, and composition of riffles that would occur naturally in the stream. I also noted the interval at which these riffles occurred, as spacing is a very important attribute for stream health.

An example of a riffle in a small stream

A second major design consideration was the organisms which lived in the stream. I conducted an organism population survey in several areas of the stream (using electrofishing and basic net-captures) to determine what types of organisms lived in the stream. The habitat preferences of these organisms, and their ability to traverse riffles of various sizes, became a guiding factor in my riffle design.

Finally, I consulted some established riffle-design equations to get a basic concept of the shape and size riffle that would be necessary to raise the flow elevation of the stream enough to reconnect it with its floodplain.

After taking all of these factors into consideration, I had developed a preliminary design, which consisted of creating 6 2-foot high riffles. The upstream slope of the riffles had a 4:1 slope ratio, while the downstream slope had a 10:1 slope ratio. The sideslope of the riffles was 8:1. All of these characteristics were determined by considering all of the factors discussed above.

Profile view of a riffle

Then, in order to determine the effect of the riffles, I constructed a HEC-RAS model of the stream. HEC-RAS is a modeling software developed by the US Army Corp of Engineers. It can model flow, floodstage, pollution and sediment transport, and more. The model was created using geographical survey information, and a somewhat complex process for determining the volume of water that the stream transmitted as a result of various sized rain events. Once the model was constructed, I was able to determine the optimal placement of the riffles, which would yield maximal impact on reconnecting the stream with its floodplain, without drastically altering the existing pattern of stream structures. Through simulating various situations by varying the size and placement of the rifflfes, I was able to finalize a design that would effectively reconnect the stream with its floodplain, without endangering any houses to flooding, and improving the habitat within the stream.

Ecological Engineering in Action: Stream Restoration

2012-01-27T15:52:00.000-08:00

Here’s the account of one of my personal projects that involved ecology and modeling that I promised:

As I discussed last time, modeling has become extremely important in ecology, as both a means of simulating potential situations, and determining ways to optimize the outcomes of any actions that one may take. This particular project centered around finding a way to stop extreme erosion that was occurring in a local stream. This stream was in a recently developed area, with houses built along it, and the erosion had quickly gotten to the point that it was threatening th structural integrity of several homes. There are several possible causes of rampant erosion in a stream/river system, but in this case it was clear that increased urbanization, and the corresponding increase in impervious surfaces, were to blame.

In an ideal situation, streams exist in a state of dynamic equilibrium, which I have mentioned before when talking about ecosystems in general. Basically, a perfectly functional stream will be a stable system, but one that is always changing. The course of the stream may slowly change, the location of various stream structures can change, but in general there is no excessive erosion or downcutting. Streams can be thrown out of dynamic equilibrium in a myriad of ways, but in this case, the area surrounding the stream was developed over a very short period of time. This development led to an increase in the amount of impervious surfaces in the neighborhood (roofs, roads, sidewalks, parking lots, etc.) and a marked decrease in surfaces that are capable of holding back large quantities of water (forests, grasslands, etc.). This led to a very sudden and very large increase in the amount of runoff (water from rain events that isn’t absorbed into the ground, plants, etc.) in the area. This increase in runoff meant that for a given size rain storm, the stream in question was forced to convey a much larger quantity of water than it had in the past.

One instance of drastic erosion along a bend in the stream

Streams are very good at adapting to new situations, and this stream did exactly that. In order to accommodate the new (much larger) loads of water that were being presented to it, it began to increase its size by eroding away the areas surrounding it. This wouldn’t have been a problem, but there were houses surrounding the stream. This prevented the stream from eroding outwards, which led to downcutting. Once the stream had downcut to a certain extent, it was no longer connected to its floodplain, and had no way to dissipate the huge amounts of energy introduced to the system whenever a large rainfall occurred (the floodplain is a crucial aspect of any healthy stream/river system. When a large rainfall/snowmelt occurs, the floodplain allows the stream to spread water out over a large area, decreasing velocity. This prevents erosion and makes the flows within the stream much less dangerous). As a last resort, this stream started eroding outwards again in order to reconnect with its floodplain, seriously threatening multiple houses.

Erosion near a couple of houses

The first step in addressing a problem such as the one presented by this stream is to scientifically determine that the stream is no longer in equilibrium, and is in fact in a dangerous failure state. In order to do this, a survey of the stream was conducted, and the results were compared to the standard characteristics of a stream in dynamic equilibrium. The results of this survey, coupled with obvious visual evidence and a measure of the amount of water the stream was conveying for a given sized rain event, made it clear that the stream was failing, and given the current circumstances, could not return to equilibrium without damaging or destroying the houses in question.

Once it was scientifically clear that this situation required intervention, and the underlying issues causing the problems were identified, it was necessary to brainstorm numerous possible solutions. Traditional civil engineering solutions, such as retaining walls, rerouting the stream, and clear-cutting and lowering surrounding areas were considered, but were determined to be either too expensive or too costly to the health of the stream and surrounding ecosystem. Instead of these traditional solutions, some innovative ecologically-inspired designs were created and considered.

Firstly, and most importantly, the severity of this situation made it clear that no single action could completely remedy the problems plaguing the area. The erosion obviously needed to be addressed, but it was also recognized that any solution to the erosion problem would mearly act as a band-aid unless the increased quantity of runoff from the surrounding community was also addressed. As such, a multi-tiered solution to the problems was created. The runoff issue would be addressed by a community-wide initiative creating a system of rain gardens and rain barrels, and properly designed retention ponds in order to reduce the amount of water coming off of impervious surfaces. Long-term, this would allow the stream to handle an appropriate amount of water, so that it wouldn’t need to increase its size.

Within the stream, an interesting approach of using natural stream structures to restore the stream to equilibrium was designed. In order to protect the bends in the stream from erosion (these are the areas that are most susceptible to erosion, and the areas threatening the houses), J-hooks were designed. These are natural stream structures, built using boulders, which gently divert the most powerful flow within the stream away from the outside banks of the stream, and into the center of the stream, where a pool is created which is an optimal habitat for many of the organisms naturally found in the stream.

Then, in order to reconnect the stream with its floodplain, a series of riffles were designed to elevate the average height of flow in the stream. A riffle is a natural stream structure where an elevated section of stream bed leads to shallow flow with high velocity, with a large amount of oxygen introduced to the water. This stream had downcut to an extent where riffles had become much more rare than they would be in a stream in equilibrium. By constructing riffles in the stream, a more natural habitat would be created, and the stream would once again be capable of dissipating large amounts of energy by expanding into its floodplain.

The final, and potentially most important step in the design process was to model the effects of the above actions. Modeling is an extremely powerful ecological tool in that it can not only simulate any given hypothetical situation, it can also help us to understand the outcome of any actions we may take, and how they would effect multiple systems. The modeling involved in this project allowed for the determination of the optimal design strategy, and ensuring that both sensitive habitats and human situations would not be negatively impacted. Through modeling, the ideal size of the riffle and J-hook structures was determined, so that they would restore the stream to a state of dynamic equilibrium, repair/improve habitat conditions in and surrounding the stream, and ensure the safety and stability of the homes in the surrounding areas. This outcome ensured the safety of valuable habitat, provided an example of a long-term solution for a fairly common type of problem, and prevented relatively large amounts of economic damage.

Profile view of designed riffles from HEC-RAS flow modeling software

In summation, this project was completed with a combination of ecological knowledge and modeling expertise. Ecological understanding led us to discover design elements that wouldn't have typically been explored, and modeling allowed us to prove that this approach would work, and fine-tune our design to have the best possible impact. This union of ecology, mathematics, and computer science seems to be an indication of both the future of ecological research, and ways in which we can make it clear that ecological principles have a real and demonstrable value in the real world.

Wildlife Corridors and Modeling

2012-01-23T20:18:00.000-08:00

This article from physorg.com ties together many of the topics that this blog will be most interested in, namely conservation, urban planning, modeling, and changes in the way ecology is studied.

The focus of this article is the new ways in which wildlife corridors are being designed. Wildlife corridors are a fairly well-accepted tool in conservation biology. The purpose of the corridors is to connect patches of habitat that would otherwise be isolated, thus allowing organisms larger roaming grounds, and preventing the detrimental inbreeding that results from complete isolation. As I said before, these corridors have been around for a while. What makes this article so interesting is the new approaches that are being taken towards designing them.

In the past, wildlife corridors were typically only utilized when there was a specific (usually endangered) species, which clearly needed a means of traversing from one patch of habitat to another. Since this was the case, these corridors were designed to meet that specific species' preferences, without much consideration given to how the corridors would effect other organisms, including humans. However, the advent of complex modeling and computational tools has made it possible for many more factors to be taken into consideration when designing these corridors. Thanks to these tools, it is now possible to design corridors while taking into consideration the preferences of multiple species, and the impact the corridor would have on humans, especially economically.

This is a new and important trend in ecology. The development not only of programs and computers that can model complex ecological interactions, but also of individuals who can grasp both ecology and engineering/computer science will be crucial to the furtherance of discovering robust solutions to environmental problems. As discussed in the article, one of the potentially most valuable aspects of new, complex models is that they can incorporate human and economic interests. If we can use models to make it clear that eco-friendly actions are also economically valuable, we can overcome one of the key criticisms of most environmentally-focused plans. Dynamic modelling of ecosystems holds the promise not only of solving eco-centric crises, but also of demonstrating to the general public the myriad ways in which these solutions could benefit them in their everyday lives.

In my next post, I'll give an example of these benefits of ecology and modelling with a real-life project that I worked on.

Thanks for reading,
Adam

Urban Ecology: An Overview

2012-01-19T10:04:00.000-08:00

Chapter 1: Applied Urban Ecology: A Framework edited by Ulrike Weiland and Matthias Richter

Here's a pretty quick read that provides an interesting (and short) overview of the history of urban ecology, and then goes on to discuss some of the major issues that the field is dealing with today.

The short history section of this reading will help provide a bare-bones familiarity with urban ecology as a field. A more detailed history is certainly worth investigating, but for my money the most interesting topic discussed here is the Odum method of analyzing urban ecosystems. This method is based on a fairly simple theory in which various aspects of a system are described as flows, sinks, and other modifiers. A flow is some quantity moving from one sink to another, and a sink is simply something in which the quantity can accumulate. For example, if we wanted to model the energy processes of a flower, flows would be solar energy, water, carbon dioxide and nutrients from the soil, and the sinks would be accumulation of biomass and energy, with an outflow of oxygen.

Another example: An basic Odum model of wolf population, with flows of

reproduction and death, a sink of population, and various modifiers to control the flow rates

The power of this method is that it is fairly easily adapted to describe nearly any system. It is equally adept at modeling an ecosystem in terms of organism populations or biomasses as it is at modeling the flow of energy or economic entities through a society. Once the basics of the "language" are understood, they can be adapted to suit the user's purpose. The language is also fairly public-friendly, in that a general understanding of the processes being modeled can be arrived at by simply following a flow chart.

The second section of the reading discusses current topics of interest in urban ecology. One of the main focuses of this section is the difficulties presented both to urban ecosystems and the study of those ecosystems by sudden, immense change. Change is a constant in urban environments, and in ecosystems. However, ecosystems tend to struggle when presented with a large amount of sudden changes. Likewise, we as scientists struggle to understand the ways in which systems react to these sudden, nonlinear changes. In a prototype ecosystem, the system functions in a state of dynamic equilibrium. In other words, fairly small changes are presented to the ecosystem, and the system as a whole adapts to these changes. Change is a driving force in a healthy, diverse ecosystem, and is in no sense a bad thing. There are also plenty of examples of nonlinear changes in nature, including fires, large storms, volcanic eruptions, floods, etc. Ecosystems are typically able to cope with these nonlinear disturbances, or if they cannot, there is usually a long enough period of relative calm after the events in which a new, functioning ecosystem can develop.

In urban settings, we are presented with an environment in which nonlinear disturbances are the norm. As such, it may be worthwhile to apply the lessons learned by studying the response of ecosystems to natural nonlinear events. We have some knowledge of the processes of primary and secondary succession in these situations (what types of organisms most easily adapt after a nonlinear disturbance, how ecosystems reestablish themselves, how long these processes take, etc.). By using this knowledge, we may be able to become more adept at modeling urban ecosystems, and understanding how they will react to various perturbences. We may even find that urban ecosystems exist in state of almost permanent secondary succession, in which the most predictable and constant aspect of the system actually is a process of nonlinear disturbance followed by abbreviated recovery.

Thanks for reading,

Adam

Optimism In Environmentalism

2012-01-17T12:36:00.000-08:00

Here's a short article from New Scientist that discusses the problems presented by the doom and gloom attitude that has come to pervade ecology and biology as of late. It makes some interesting points on the effect that this attitude has on the public perception of environmental issues. As such, it seems like as good a place as any to kick off this blog. Ecological Perspective will focus on key issues in ecology, urban planning, and engineering, but will also branch out into discussions of current and past projects I have worked on, music, travel, outdoor activities, etc. The unifying thread, and the concept behind the blog will be that each topic will be addressed from an ecological/environmental perspective, with a mind to be both inviting to the general public, and thought-provoking to those more well-versed in environmental fields. Here goes nothing...

Getting back to the article linked above, it is a widely accepted fact, especially in scientific communities, that environmentally, our planet has fallen on hard times. There's the typical litany of global warming, pollution, and extinctions so widespread that there's a legitimate claim for humans being the driving force behind an extinction event rivalling the magnitude that destroyed the dinosaurs. Not pleasant reading.

Evidence of human impacts can be inescapable even on short camping trips:

An entire stand of trees wiped out by an invasive parasite

However, as this article discusses, it is important to not only make the general public aware of these crises, but also to share the wealth of inspiring stories and accomplishments that draw people to nature and careers in the environment. People are naturally drawn to stories of accomplishment, of disasters averted, lives improved, and lasting happiness. This is why so many of our best and brightest are drawn into the medical field. We all know the scourges of modern disease, but time and again individuals choose to take up the daunting task of trying to cure extremely complex diseases because they have heard success stories, and so dare to hope for more success. Having worked in medical research, I have seen firsthand the dogged determination with which researchers labor, driven on by a knowledge of the impact their work could have.

In the environmental field, we have become so focused on ensuring that people appreciate the gravity of our catastrophes that we have forgotten how important, and how much stronger a motivating factor, inspiration is than condemnation. We need to not only showcase our accomplishments, but also to remind people of the value of what we are working to preserve. Before people will care about losing natural spaces, they must first appreciate their value. To this end, environmentalists should focus more effort on introducing others to the things that attracted us to this field in the first place. Things like camping trips, encountering an exciting animal, fishing in a pristine lake, canoeing on a healthy river, the list could go on endlessly.

It is also important that we elucidate the value of the potential effects working towards saving the environment could have. There are the obvious and direct benefits of saving species, preserving habitat, clean air and water, etc., but there are also numerous indirect benefits that could come along the way to these more direct goals. Once we can make it clear that the environment is both worth saving and save-able, I believe we will see a marked increase in both public interest, and the amount of people who cannot wait to dedicate their lives to preserving nature.

Thanks for reading,

Adam