April 24, 2015
Kate Gazzo, M.S.
As an ecologist understanding how changing climates affect restoration can be essential to a project’s success. Questions which arise include; how likely is a restored wetland to remain wet in an increasingly Mediterranean climate, and what is the success of restoring a tidal marsh along a coast that is predicted to be underwater in 100 years? Considering millions of dollars are often spent on restoration projects, the projected biophysical conditions of a project region should be considered to secure the long-term success of a project and protect the financial investment that has been made to restore a site.
Results produced from mapping biophysical shifts within the U.S. show that half of ecosystems will be unable to maintain historical conditions, as a result of increased greenhouse gas emissions and will experience changes in soil, temperature, and/or precipitation (Figure 1). In many areas of the U.S., predominantly in the south and much of California, dry areas are predicted to become increasingly arid, while wet areas such as the Pacific Northwest will receive increased precipitation.
How is climate change affecting vegetation communities?
One of the biggest restoration concerns stemming from climate change is the long-term stability of vegetation communities. While specific effects at any scale (community, population, or species) are hard to predict due to plant adaptations and migration rates, some consistent predictions exist. These include: poleward shifts, upslope elevation shifts, and replacement of native species with invasives which are tied to long term changes in temperature and precipitation patterns (Walther et al. 2002).
Vegetation communities will experience latitudinal or, poleward shifts, as a response to long term changes in temperature and precipitation. Examples of poleward shifts include the appearance of shrubs in prior shrub-free regions of Alaska and predicted northward advancement of eastern tree species by as much as 250 km- a change that would lead to these species no longer having ranges within the U.S. (Iverson and Prasad 1998).
Elevation shifts are another effect resulting largely from changes in temperatures and also precipitation patterns. These shifts are oftentimes upslope and occur as plant communities shift into more suitable temperature ranges. Unfortunately, for vegetation communities distributed along ridges and mountaintops which are nearing their temperature and precipitation thresholds, there is no suitable habitat for these communities to shift to. Vegetation communities that are particularly at risk are alpine/subalpine and conifer forests. Within California, warmer temperatures are predicted to have a significant effect on the percentage of alpine/subalpine (-77%) and conifer (-51%) forests as these communities are pushed out of current habitat ranges (Figure 2).
In addition to changes in plant community distributions, plant community compositions will also change. As the ideal habitat range for native species shifts, we will likely see competitively dominant invasive species replace native species. For example, in Arizona, prolonged drought over the past twenty years has already been attributed to widespread pinyon pine mortality and invasion by juniper (a native species dominant in lower elevations) (Mueller et al. 2005).
Integrating Climate Change into Planning and Restoration
Because the success of restoration projects largely depends on the survivorship of plant communities, climate change planning is being increasingly incorporated into planning and design of projects. Effective planning requires additional consideration of the future biophysical conditions, not just historical and current conditions when forming restoration goals. Future climate scenarios are derived from mathematical representations of the interactions between the earth, ocean, and the atmosphere which calculate changes in precipitation, sea level rise, temperature, and other variables over time.The Coastal Vulnerability Index (CVI) is one example of a model which maps coastal areas most at risk to Sea Level Rise (SLR). This particular model was used by Great Ecology to assess SLR impacts at three locations within the New York-New Jersey Harbor Estuary. Results from modeling were then used to form recommendations to build resiliency at each location.
In addition to modeling, there are a number of other techniques that restoration managers can implement to ensure the long term success of projects, these include:
While we may not be able to predict human actions such as how much or how little carbon emissions will change in the forthcoming years, we can assume that climate conditions will change. And as restoration practitioners we can continue to incorporate variability into plans to create more resilient and sustainable habitats.
About the Author
Kate Gazzo is an Ecologist based in Great Ecology’s Sacramento office. She specializes in water quality issues and watershed management with experience in invasive species management, wetland delineations, and biological surveys. She recently conducted water quality monitoring associated with agricultural contaminants in California’s central valley.
Lenihan, James M., et al. “Response of vegetation distribution, ecosystem productivity, and fire to climate change scenarios for California.” Climatic Change 87.1 (2008): 215-230.
Louis R. Iverson and Anantha M. Prasad 1998. Predicting abundance of 80 tree species following climate change in the eastern United States” Ecological Monographs 68:465–485.
Lavendel, Brian. “Ecological restoration in the face of global climate change: obstacles and initiatives.” Ecological Restoration 21.3 (2003): 199.
Mueller, Rebecca C., et al. “Differential tree mortality in response to severe drought: evidence for long‐term vegetation shifts.” Journal of Ecology 93.6 (2005): 1085-1093.
National Park Service. “Pinyon-Juniper Woodlands-Climate change and Literature Cited”. Accessed March 26, 2015 from http://www.nps.gov/articles/pinyon-juniper-woodlands-climate-change-and-literature-cited.htm
Saxon, E., B. Baker, W. Hargrove, F. Hoffman, and C. Zganjar. 2005. “Mapping environments at risk under different climate change scenarios”. Ecology Letters 8:53–60.
Veloz, S. D., N. Nur, L. Salas, D. Jongsomjit, J. Wood, D. Stralberg, and G. Ballard. 2013. “Modeling climate change impacts on tidal marsh birds: Restoration and conservation planning in the face of uncertainty”. Ecosphere 4(4):49.
Walther, Gian-Reto, et al. “Ecological responses to recent climate change”. Nature 416.6879 (2002): 389-395.Leave a comment
April 23, 2015
San Diego citizens, communities, and corporations will come together this Saturday, April 25th at 106 different locations around San Diego County to address the dilemma of marine debris at the source – the creeks, rivers, and watersheds that flow to the ocean. The 13th annual Creek to Bay Clean Up, is organized by the I Love a Clean San Diego organization, a local non-profit dedicated to the conservation and preservation of natural resources through activism and community education.
Come join Great Ecology staff and friends this weekend as we try to beat last year’s record of 100 tons of trash collected! With over 100 different locations you won’t have to travel far to participate in this community event.
Find a location near me
April 17, 2015
Joseph Cherichello, PLA
It is springtime in New Jersey, the Garden State, and there are nearly fifty seedlings growing in pots on our kitchen table. Soon we will gradually introduce them to the outdoors to harden off, and give us full access to our table again.
We have been growing a vegetable (technically, mostly fruit I suppose) garden every year for the past seven years. At first we had a modest 10×10 area with a temporary fence, and as many plants as we could reasonably fit: mainly tomatoes, peppers, and lettuce. Then, as we began expanding our garden, I started looking for ways to improve it. I would think back to the days when my grandfather had his garden, and try to remember how he did things. I remember he grew tomatoes, hot peppers, lettuce and cucuzza; an Italian squash the size of baseball bats, but what were his methods? At the time he was around, I honestly wasn’t really that interested in how he did things. I just knew, that was his garden, and if you weren’t in there helping, it was time for you to leave. Thinking back, I can understand why he didn’t want anyone messing around in his garden, and I now appreciate how successful and tidy it was. The one thing I do remember about his process was that he used pigeon manure from his neighbor’s pigeon coop as fertilizer. Any grandkid that heard this was sure to be grossed out.
A Permaculture-type Method
So, without my grandfather’s advice on hand to guide me (or a stash of pigeon poop nearby) I needed to research and learn by doing. Being a Landscape Architect, and having a great interest in ecological design, I began sketching designs for my garden structure and plant layout, and planning how I can be environmentally conscious about it. To me this meant no herbicides, no pesticides, no chemical fertilizers, sowing seeds from a local source, and reducing water usage.
My first goal was to find a source for compost. I didn’t have time to make my own (which we eventually started doing) because I needed a lot. I found a source for quality mushroom compost the next town over, which I learned, is not easy to come by. I ended up building a 13×24’ fenced in garden area with trellises for climbers, and a sitting area to relax in the anticipated shade of grape leaves. I removed the top six inches of the sandy ‘native soil’ (a mix of native soil, construction sand and debris) to reduce the seed bank of weed species. I laid four layers of newspaper down (in an attempt to prevent other plants from popping up), and covered it with 6” of compost. I refrain from tilling or turning over the soil to keep the soil structure intact. This process was my attempt at eliminating the use of herbicides. Inevitably, weeds find their way growing where you don’t want them (the definition of a weed), but this process seemed to reduce the amount, and the ones that I did have were easily pulled by hand.
Another advantage to using the mushroom compost (I lay two to three inches down each year) is it is a natural fertilizer. This eliminates the need for chemical fertilizers, which can leach past the roots, becoming unavailable to the plants and possibly contaminating the groundwater. The plants seem to be happy with it.
Minimizing Water Usage
After setting up the soil layer, I installed a drip irrigation system. It attaches to a typical spigot and in combination with a timer, gives many options for regulating the amount of water used each day. The lines of ¼ inch hoses have emitters every 6 or 12 inches, which are laid along the rows of plants and disperse a specified gallons per hour (typically 0.5). Usually after the plants are established, watering for 45 minutes every other day seems sufficient in my region. Emitters up to 2.0 gallons per hour can be attached to the ends of lines for blueberries, grapes, or plants that require more water.
This not only reduces wasteful watering by concentrating the application to the root zone, but it also reduces mold and fungus on susceptible plants like tomatoes and zucchini, since the drip does not splash up spores from the soil to land the lower leaves. The only time the irrigation system would need attention is to shut if off when it rains (and to turn it back on of course). There are timers with rain sensors that will turn the water on and off depending on the weather, but they are quite expensive.
As I mentioned earlier, much thought goes into the layout of the plants. Not only do you need to think about how big each plant will get, you also need to think about how you will be able to access them to say, string up your tomatoes or comfortably harvest the crop. Spacing is very important. I have spent the past 10+ years as a Landscape Architect determining the proper spacing of various plant material, but it takes great strength to refrain from overcrowding my vegetable garden. I always want more! (Solution: I am taking down a section of fence and adding another 80 square-feet.)
To complicate matters a bit further, some crops should be rotated each year. Tomatoes, peppers, eggplant, and potatoes are members of the nightshade family (Solanaceae), and should not be planted in the same location as the previous year (this includes other plants in the nightshade family as well). This helps prevent the build-up of microbes in the soil harmful to those specific plants.
Eliminating the Use of Pesticides
To eliminate the use of pesticides, we incorporate companion plants and use cultivars that are less susceptible to disease. (Cultivars are a hybrid of cross-pollinated similar species. Very different from GMOs (genetically modified organisms), but that is a blog for another time).Having species that are less susceptible to disease can reduce the number of pests, since pests typically will be attracted to and attack stressed plants. But, for the pests that will likely come to feast on any plant, planning for and planting companion plants can help. For example, bush beans will not only fix nitrogen (take nitrogen from the air and convert it to a form in the soil available for plant use), but if planted among eggplant, can also protect eggplant from the Colorado potato beetle. Similarly, planting garlic under a peach tree can repel peach tree borers. Or, planting marigolds in and around the garden discourages many harmful insects and nematodes. One can see how this can take a lot of planning, but really, you have all winter to do it.
Finally, to attract pollinators, we surrounded our garden with perennials native to the region;
Echinacea purpurea (purple coneflower), Liatris spicata (dense blazing star), Rudbeckia hirta (black-eyed Susan), Solidago sempervirens (seaside goldenrod), Eupatorium coelestinum (blue mistflower), and Monarda fistulosa (wild bergamot) to name a few. This not only attracts pollinators and enhances the aesthetics of the garden, but it also ties the garden space into the rest of the landscape.
New for us this season, we will be making compost tea. This is a process where compost is placed in a burlap sack, and soaked in water in the sun for a couple of days (same way you would make sun-tea I’d imagine, but less refreshing). Then we’ll use that tea to fertilize the plants. This is supposedly another great alternative to chemical fertilizers. Seems like it will be, but again, this garden is and has been a learn-by-doing process. So, we will see.
Reaping the Rewards
There is great satisfaction in having a successful garden; producing enough food to last for months, canning tomatoes to make gravy (yes, gravy), sharing our crop with family and neighbors, and knowing that it is done in an environmentally conscious way. However, the most rewarding aspect of all this is that is a family garden. Together we sow seeds, plant plants, and harvest our crop (my son is worse than the birds, eating every blueberry or strawberry he can pick). Though my grandfather has never seen my garden, and knowing how much he was a family man, I can be sure that he would be proud.
About the Author
Joseph Cherichello is a Certified Professional Landscape Architect with over ten years of experience in land development, emphasizing ecological design, urban forestry and stormwater management. He currently provides construction oversight and public access design for a 185-acre brownfield redevelopment and wetland restoration project.
April 16, 2015
Great Ecology is excited to announce that Senior Ecologist, Dr. David J. Yozzo, will be chairing a session on Ecological Restoration this Sunday, April 19th, at the Northeast Natural History Conference.
In addition, Dr. Yozzo will be presenting, “Ecological Restoration in New York City: Challenges, Opportunities, and Experimentation.” He will address some of the unique challenges facing densely populated and industrialized urban settings, such as the New York City metropolitan area, and how ecologists, environmental engineers, and restoration practitioners can respond to create innovative, resilient ecosystems.
The Northeast Natural History Conference, now in its 15th year, is an interdisciplinary forum for individuals to present the current best practices and latest research on applied field biology (freshwater, marine, and terrestrial) and natural history for the Northeastern United States and adjacent Canada.Leave a comment
April 11, 2015
In 2005, when Richard Louv published his influential book Last Child in the Woods, there was no statistical evidence to show that society was spending less time in nature. Anecdotally, however, Americans could see that their growing appetite for television meant less time out of doors, and as a result, Last Child in the Woods galvanized support to promote outdoor play and to ‘get children back in the woods’.
Last Child in the Woods explained that outdoor play was crucial for child development and there is a substantial body of research describing the cognitive benefits of nature-based play. As one study, “Creativity in the Wild: Improving Creative Reasoning through Immersion in Natural Settings” explains, nature is rejuvenating for the mind.
“Our modern society is filled with sudden events (sirens, horns, ringing phones, alarms, television, etc.) that hijack attention. By contrast, natural environments are associated with a gentle, soft fascination, allowing the executive attentional system to replenish. In fact, early studies have found that interacting with nature (e.g., a wilderness hike) led to improvements in proof reading, control of Necker Cube pattern reversals, and performance on the backwards digit span task.”
The proof that Americans were in fact spending less time in nature came two years later in an article titled “Evidence for a Fundamental and Pervasive Shift Away from Nature-Based Recreation,” which analyzed large data sets like National Park attendance. The article described how the number of visitors to U.S. National Parks had grown for decades, and then in the late 80’s the trend reversed, and attendance began to decline.
U.S. National Parks were not the only indicators to show this phenomenon. Fourteen other data sets considered proxies for our time spent in nature, ranging from Hunting and Fishing Licenses to through-hikers on the Appalachian Trail, all showed a correlated decline. These 14 data sets lost on average 18% to 25% of participants per capita between 1989 and 2007.
Louv and others identified a problem ̶ we are spending less time in nature, something crucial to child development and perhaps society as a whole. To fix this problem, however, we need to understand how our relationship with nature is changing. How our society’s cultural makeup, level of technology, population density, and time availability has changed our preferences for outdoor activities. Luckily surveys conducted by the U.S. Forest Service begin to tell this story.
According to the Forest Service’s periodic recreation surveys, the number of total participants in traditional activities such as hunting and fishing has levelled off over the last three decades (a per capita decline). In their place photographing birds emerged as the fastest growing nature-based activity, growing 287% from 1982 to 2007. There are now more birders than hunters and anglers combined. Day hiking (210%), backpacking (161%), off-road motoring (142%), walking outdoors (111%) and canoeing/kayaking (106%) have also shown growth.Looking forward, the Forest Service predicts that developed skiing, visiting interpretive sites, day hiking, birding and equestrian activities will show the most dramatic growth by 2030. Conversely, the five activities expected to grow the least are hunting, motorized snow activities, off-road motoring, floating and fishing.
One very important trend is our growing desire to learn about nature, evident in the fastest growing sector, the so-called “Nature Appreciation Activities” (e.g. visiting interpretive sites and photographing wildlife). Our time spent in wild areas is not simply to get away from the hubbub of modern life, though many people still identify this as an important aspect of their time in nature, a growing portion of society also enjoys learning about these environments. While any growth in nature-based recreation is beneficial, the desire to learn about these ecosystems bodes especially well for our role as stewards of the environment.
An inherent challenge in promoting Nature Appreciation Activities is that the most interesting and pristine ecosystems are also easily degraded, a dilemma of eco-tourism. The impacts from nature-based recreation are a function of the frequency of use, the type and behavior of use, season of use, environmental conditions, and the spatial distribution of use. And compared to traditional nature-based recreation, such as hunting and fishing, Nature Appreciation Activities often gather participants in relatively high densities. Where trampling is intense it reduces plant height, plant cover, and species richness and shifts the species composition of the community. While these disturbances rarely impact the function of the ecosystem as a whole, they can drastically change the experience, especially for visitors interested in rare plant communities or the insects, birds, and mammals associated with them.
One way that we can encourage the long-term growth of Nature Appreciation Activities is by constructing trails that provide access to a variety of natural environments while protecting plants and soil from unintended disturbance. Fortunately, human kind has a long history of trail building to draw from, and with new materials, construction techniques, and ecological knowledge we are well positioned to support low-impact, meaningful interactions with nature – with trails that tiptoe through lush vegetation or sensitive plant communities; provide glimpses of rare habitats without bisecting them; and even change our vantage point, lifting us off the ground into the forest canopy. Creating this Nature Appreciation infrastructure allows visitors to access a variety of ecosystems and biodiversity. This is one way that we can help counter the decline in nature-based recreation and environmental degradation, so that in the coming decades we may continue to enjoy the extensive benefits of time spent in nature.
About the Author
Charles Howe is an environmental scientist and landscape designer specializing in wetland ecology, ecosystem restoration, and site planning. Currently, Charles is supporting the design, permitting, and Environmental Site Assessment of a tidal wetland mitigation and habitat creation project along the East River in New York.
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April 7, 2015
We are excited to announce our Senior Biochemist, Dr. Ioana G. Petrisor will be a Keynote Speaker at the 2015 Used Oil/HHW Conference on April 8, 2015. Dr. Petrisor will present new, state-of-the-art fingerprinting techniques, applications, and recent research. She will share techniques to help track sources of illegal dumping as well as how to evaluate and distinguish used (“fake”) motor oil.
This year’s theme focuses on “The Reduced, The Reused and The Recycled” detailing innovative approaches and best practices for waste management from oil spills to hazardous household waste.
The annual CalRecycle conference unites nonprofit agencies, federal and state agencies, private businesses, and others who are involved in used oil recycling and concerning resource conservation and the appropriate management of used oil, household hazardous waste, pollution prevention, and other toxins.
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April 1, 2015
Jeffrey Harlan, Esq., LEED AP
“Whiskey is for drinking; water is for fighting” – attributed to Mark Twain
Twain knew a thing or two about California’s culture and politics, and his prophetic words have become all the more poignant in the last year. The Golden State is in the midst of its fourth year of severe drought, with snowpack in the Sierra Nevada Mountains—a significant source of freshwater for the state— at historically low levels.[i] While communities and water districts across the state have been implementing their own water conservation measures—restricting outdoor residential irrigation, offering financial incentives to replace thirsty lawns with drought-tolerant landscaping, and issuing steep surcharges for exceeding allowed limits—the state government has finally taken the regulatory plunge.[ii]
The Sustainable Groundwater Management Act of 2014
Last September, California Governor Jerry Brown signed into law the state’s first regulations on groundwater resources – the Sustainable Groundwater Management Act of 2014 (SGMA).[iii] Up to this point, California was the only western state that did not have comprehensive regulations for groundwater. Groundwater accounts for about 40 percent of the state’s total annual water supply.[iv]
SGMA creates a framework for sustainable, groundwater management, providing local agencies the authority to adopt groundwater management plans tailored to their community’s conditions and needs. The legislation applies only to “high and medium priority” groundwater basins (127 out of 515 in the state), which account for approximately 96 percent of the groundwater use in California. The state’s approximately 30 adjudicated basins (i.e., where water rights in a stream system have been determined by a court) are exempt from the new legislation.
SGMA Details: Focus on Local Control
The intent of SGMA is to provide state government a limited role, allowing it to intervene only if local agencies cannot meet specific deadlines and conditions. The State Water Resources Control Board will supply technical support and $100 million of funding (from Proposition 1, the recently passed state water bond) for planning and implementing groundwater solutions.
Specifically, SGMA requires:
1) New local groundwater sustainability agencies to be formed by 2017;
2) The development of groundwater sustainability plans by 2020 for overdrafted high and medium priority basins (by 2022 for other similar basins not in overdraft); and
3) Each high and medium priority basin to achieve “sustainability” by 2040.
And, of paramount importance to landowners, the legislation expressly preserves their water rights.
Implementation: Implications for Planners, Users, and Communities:
It is certainly too early to raise a glass of whiskey and toast the law’s success. SGMA is in important first step, but as it becomes implemented across the state a number of complex questions will surely bubble to the surface.
About the Author:
Jeff has over 15 years of experience as a community planner, specializing in sustainable development, strategic planning, and environmental design. He brings a unique perspective to challenging land use and regulatory problems, shaped by his experience as a deputy to an elected official, and planning director for a California state land conservancy.
[i] Electronic readings by the Department of Water Resources (DWR) in March 2014 indicate the water content of the northern Sierra snowpack is 4.4 inches, 16 percent of average for the date; the central and southern Sierra readings were 5.5 inches (20 percent of average) and 5 inches (22 percent) respectively. California Department of Water Resources, http://ca.gov/drought/, March 3, 2015.
[ii] Water Districts have adopted a number of mandatory restrictions and prohibitions. http://www.acwa.com/content/local-drought-response
The State Water Resources Control Board adopted new restrictions on March 17, 2015, including limiting outdoor residential irrigation, requiring restaurants only to give water to patrons when asked, giving hotel guests the option to not launder sheets and towels daily.
The City of Los Angeles incentivizes with lawn replacement program for residential and commercial properties ($3.75/sq. ft. for residential).
[iii] The Sustainable Groundwater Management Act is actually a three-bill legislative package, composed of AB 1739 (Dickinson), SB 1168 (Pavley), and SB 1319 (Pavley).
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March 27, 2015
Over the past three decades, thousands of contaminated sites have been assessed and remediated through the EPA’s Superfund program, and many are currently on the program’s National Priorities List awaiting assessment and cleanup. Remediation of contaminated sites and spills is still a major concern in the U.S. and technology is improving to address needed cleanup. In the past, scientifically-proven methods of remediation generally involved engineered technologies, such as removal of materials to a landfill or pump and treat systems, which can be very costly. Technologies that utilize naturally occurring organisms to mitigate or remove toxic substances from soils and groundwater are increasingly being studied and employed on contaminated sites. These technologies, known as “bioremediation,” can offer advantages over conventional methods, including potentially lower costs and less transport of hazardous materials.
Bioremediation has been used to treat a number of organic and inorganic contaminants in the environment including hydrocarbons, chlorinated chemicals, pesticides, metals, and other contaminants. Various treatment methods may be used depending on the chemicals of concern, but most generally employ microorganisms to reduce toxic potential. Microbes, for example, can be applied to contaminated soils where they metabolize contaminants into less toxic forms (Donlon and Bauder 2015).
Phytoremediation, a similar kind of natural remediation, uses plants for decontamination and has demonstrated effectiveness at former mines and industrial sites. The method is attractive because it enables remediation at the site (in-situ) without transport of soils and can be performed at a relatively low cost. Plant species with faster relative growth are used to speed up the phytoremediation process. In particular, species of willow have been studied due to their rapid growth and premature foliation (Université de Montréal 2011). A recent study in Finland looked at the ability of different species of willow, with varying degrees of phytoremediation capacity, for remediation of heavy metals at a mine site (University of Eastern Finland 2014). The observed species which exhibited the best results was Salix schwerinii, as well as a hybrid of Salix schwerinii and Salix viminalis. These projects are helping to isolate the most efficient species of plants, as well as ideal proportions of microorganisms, to speed up site decontamination.
Although bioremediation is a well-known process, a number of studies are being performed aimed at making remediation potential faster and more effective, with fewer toxic byproducts. In the case of phytoremediation, the key seems to be identifying plant species that perform decontamination most effectively and expeditiously. Phytoremediation may have limitations however, which requires understanding of local conditions, including soils and local ecology to design effective remediation strategies. However, the potential for creating more cost-effective remediation that minimizes earth-moving is significant (University of Eastern Finland 2014) – not to mention the aesthetic benefits of a greener landscape.
About the Author
George Patten is an environmental scientist with experience in water quality assessments and watershed planning in Colorado. He has extensive experience assessing ecological and human health risks of contaminated soils, sediments, and groundwater. George also has a strong background in geospatial analysis, GIS, and other data visualization tools.
March 26, 2015
Great Ecology’s Senior Biochemist, Dr. Ioana G. Petrisor directed a workshop this week on “Classic and Emerging Environmental Forensics Techniques and Applications” at the Association for Environmental Health and Sciences (AEHS) conference in San Diego. This workshop reviewed classic and emerging forensic techniques used for age-dating, source identification, and cost allocation, emphasizing on effective strategy building from both scientific and legal perspectives.
Cutting-edge forensic techniques such as chiral fingerprinting, position-specific isotopic analysis (PSIA), mineralogical fingerprinting and dendroecology (tree-ring fingerprinting), were discussed and presented through several international case studies including:
• Evaluating the source of gasoline samples through focused fingerprinting (combining information from chemical and isotopic fingerprinting);
• Distinguishing between closely related crude oils by targeted fingerprinting focused on n-alkanes, Pristane, Phitane and certain biomarkers (isomer pairs);
• Establishing site specific clean-up limits at an historical foundry in France using mineralogical fingerprinting (combining scanning electron microscopy with chemical elemental analysis);
• Determining the occurrence and age of middle distillate releases at a historical gas station in the U.S.
Ioana G. Petrisor, Ph.D.
Dr. Petrisor is a biochemist with 21 years of experience, specializing in environmental forensics and litigation support. She is a member of the AEHS Scientific Advisory Board and a forensic instructor for the organization. Dr. Petrisor has served as an expert witness in California, testifying on issues associated with environmental contamination.
March 12, 2015
Alejandro Baladrón Julian, M.S.
Did you know that small amounts of pollution can dramatically change the species composition of a natural habitat? Biodiversity indicators are excellent tools for assessing which way landscape units are heading in terms of habitat quality. Biodiversity can be easily calculated by using rapid assessment indicators such as species richness and species diversity indices. By comparing results across landscape units, we can predict biodiversity patterns, detect management gaps in natural areas, or implement appropriate conservation planning guidelines. However, results obtained through the use of rapid assessment indicators require cautious interpretation. Sometimes it is assumed that habitats exhibiting very high values of species diversity are of excellent quality. However, that assumption is not always correct.
Understanding Disturbance & Species Diversity
All species have tolerance limits for environmental factors beyond which individuals cannot survive, grow, or reproduce. Disturbance sources, such as pollution and land use changes, can disrupt normal ranges of environmental factors affecting biological communities. Biomonitoring protocols help measure the quality of habitats by studying the attributes of biological communities, including their diversity in terms of species taxa or functional groups. However, the relationship between biodiversity and intensity or frequency of disturbance is not always linear, as is depicted in the parabolic graph (Fig.1) of the Intermediate Disturbance Hypothesis.
Fig. 1. Graph showing variation of diversity with disturbance according to the Intermediate Disturbance Hypothesis: a) low levels of disturbance allow competition reducing diversity; b) greatest biological diversity occur at intermediate levels of disturbance as a result of loss of the most sensitive species and invasion of opportunistic species; c) high levels of disturbance reduce diversity.[/caption]
Low Intensity Disturbance
Physical disturbance prevents a competitively dominant species from excluding other species from the community, and there is a trade-off between a species’ ability to compete and their ability to tolerate disturbance. For example when disturbance conditions in a river are of low-intensity or infrequent, species diversity may also be low because only the best competitors persist. Headwater streams are usually good places to find highly specialized pollution-intolerant taxa including giant stoneflies and flathead mayflies, as long as there are no cattle or other sources of disturbance.
High Intensity Disturbance
When disturbances have a high intensity, diversity is reduced through the loss of species that are particularly sensitive to disturbance, which tend to be native species well-adapted to pristine conditions. For instance, streams draining heavily urbanized catchments are almost always exposed to high disturbance regimes due to frequent pollution loads entering the streams through sewer systems. As a result, macroinvertebrate communities in urban streams are usually dominated by large numbers of pollution tolerant taxa including tubificid worms, leeches, moth flies, and rattailed maggots.
Moderate Intensity Disturbance
Disturbance scenarios of moderate intensity have been widely discussed in scientific literature because of their implications for species diversity. At intermediate levels of disturbance, there is a balance between competitive exclusion and loss of competitive dominant species due to disturbance. In this scenario, conditions favor the coexistence of competitive species and disturbance-tolerant species. As a result, a peak in diversity may occur at intermediate intensities of disturbance.
Streams affected by moderate intensity disturbances can show an array of native aquatic invertebrates. The majority are usually competitively dominant, with the addition of a few opportunistic species, which are usually benefited by increased disturbance. Ecologists have observed certain streams located on agricultural lands with the ability to support a high diversity of aquatic invertebrates, as long as they are not affected by aggressive practices like the excessive use of pesticides in row crops.
When we evaluate water quality conditions of streams by analyzing macroinvertebrate-based bioindicators, higher diversity may be found in slightly polluted sections of the stream rather than in pristine sections, where we may find only native species. Therefore we may incorrectly conclude that overall habitat quality is higher in polluted sections like those affected by stormwater outfalls. An incorrect interpretation of biodiversity results would prevent us from providing an accurate stream assessment of water quality status.
Analyzing and Interpreting Biodiversity Data
Rapid assessment biodiversity indicators, such as species richness and evenness, can significantly reduce costs of environmental studies and are strongly recommended for pilot or reconnaissance studies. However, their capacity to detect differences in habitat quality is sometimes limited and may not fulfill the most demanding project goals. Rapid assessment procedures can be substituted with studies based on hypothesis testing, replicate samples, and multivariate analysis approaches which increase the accuracy of results but also raise project costs.
It is also possible to increase the reliability of results and reduce projects costs by using multiple diversity and community composition indices to assess habitat quality. For example, Great Ecology uses a comprehensive set of benthic metrics to periodically assess the quality of restored open water habitats and tidal areas at the Woodbridge Waterfront Park project site in New Jersey. Benthic metrics are measurements of the structure, function, or other characteristics of the macroinvertebrate community that change in some predictable way to increased disturbance. Our set of benthic metrics includes measures of species richness, diversity, dominance, presence/absence of tolerant or intolerant species, functional feeding groups, and macroinvertebrate-based indicators of water quality. A broad spectrum of metrics provides more accurate information to address our clients’ restoration goals as compared to using just species richness and diversity indices. Understanding what makes a quality habitat requires an awareness of local disturbances and a comprehensive knowledge of the best practices to approach each particular case.
About the Author
Alejandro Baladrón Julian is an environmental scientist specializing in hydrology. He has extensive experience performing Environmental Impact Assessments and hydrology modeling, including the design of drainage networks for highway and railway lines, the analysis of evacuation capacity in wastewater drainage systems, and flood risk studies.