It's Tough

I was thinking of the topics I could write about today, and what came to mind made me step back and think: "This is why lots of people don't read environmental blogs. The subject matter always seems to be depressing." I decided to start blogging again because I felt, as I did previously, that it is important to highlight the environmental issues that exist. Some topics are more uncomfortable than others to deal with, but I have tried to make it a policy in my life to not hide from the dark realities that are out there.

But why does it seem there are more negative environmental topics to write about than positive-feel-good topics that make us feel all warm and fuzzy inside? Unfortunately that is reality. There are great environmental stories to write about that discuss things such as conservation success stories, a species being saved from near extinction, the discovery of a new species, resilience after an environmental disaster, etc. However, for each one of those news items, there are at least two that highlight the sorry state of affairs our global environment is in.

Part of that lies in the fact that nature has always been a very tough "mother". Stephen Fry said it best a few years ago, remarking, "You have to account for the fact that almost all animals in the wild live under stress with not enough to eat and will die violent and bloody deaths. There is not any way that you can just choose the nice bits . . ." (Fry, 2009). Yes, if you reference that quote online, you will find Stephen Fry is talking in terms of atheism/proving the existence of God, but I feel that it fits here. The environment is a rough and tumble place, undergoing constant (though sometimes slow) and chaotic change, punctuated by abrupt, violent episodes of natural disaster. It is amazing and complex, and I am always left in pure amazement by all this planet has. Despite this, it has always dealt biological life some depressing cards.

Beyond the day-to-day reality that the environment is a tough place that taken alone will have plenty of depressing stories, is the fact that we as the human species have been and are the cause of many of the depressing changes in the global environment. Sometimes our activities are indirectly causing these negative changes, such as the disappearance and stress put upon coral reef ecosystems due to sea level rise/increase in carbonic acid in oceans which is linked to climate change. Others are directly linked to our activities such as oil spills, climate change, the near-extinction of many species of plant and animals, etc.

We will always have an impact on the environment. That is how biological life works. Plus, we don't always know when we are having a direct or indirect negative impact on the environment. Thankfully, science exists to help us determine what is influenced by our impacts on the environment. When it comes down to it, I often write more about these alarming topics because only when we become informed of an event and what it is we are (not) doing, can we begin the path of changing. I believe strongly in the ability of humans to move away from destructive habits when they are educated about what it is we are doing wrong. I believe in our ability to address the issues we face through innovation and corrective action. That is why I always urge some sort of action on our part at the end of each post.

Writing about and caring about the environment is tough. At every turn there is another disheartening story of a species going extinct, a major industrial accident that has significantly impacted a local ecosystem, or climate change deniers preventing meaningful change in how humans consume energy. I remain dedicated to the environment not just because it is the only thing we've got, but because it is something unique and special. The type of life and the varied ecosystems it thrives in on this planet is spectacular. What's more, we are a part of it and because of our intellect we have the ability to correct our course of action before things go horribly wrong. It may be depressing to read all the bad news, but the bigger picture I see is that we can stop more depressing news from reaching us by acting now on the knowledge we are acquiring. The truth, in this case, can indeed set us free on the path to conserving all our planet has to offer.

Sometimes Pictures Really Are Better Than Words

I read an article on the online version of The New York Times this morning about increased melt from glaciers and the Antarctic ice sheets. The first image they had reminded me of all the other pictures I have seen of glaciers retreating. For me, these pictures give powerful voice to the evidence that scientists have acquired that the world is warming. It's not just one glacier, it is all of them. Here are some pictures that really do speak louder than words that global warming/climate change is real.

Upsala Glacier

Portage Glacier

Pederson Glacier

Rhone Glacier

McCarty Glacier

West Rongbuk Glacier

Lunacy and Money

My last post briefly mentioned that there may be a reason why people are not responding to the facts that climate change is indeed happening. We may be evolutionarily ill-equipped to deal with long-term, long-range threats because of our brain habits. There is that, but then there is the fact that plenty of leaders, both business and politicians pour money and rhetoric into discrediting climate change along with meaningful action to mitigate it. Today's post looks at the latter.

I was scrolling through Huffington Post today when I came across this article stating that a House Republican added an amendment to a Military Budget bill that forbade any usage of the ascribed funds to research the threats associated with climate change. The bill and amendment passed thanks to all Republicans and four Democrats voting in favor of the measure. The actual amendment is peppered with Tea Party and climate denial catch phrases such as Agenda 21 and the IPCC Fifth Report. No funding provided by the US government may be used in any research that may actually validate and assess the threats posed by climate change. This comes despite the fact that the Defense Department has repeatedly acknowledged the threat that climate change poses to national/global security and its military operations around the world.

So who is the House Republican that was behind this short-sighted amendment? It is none other than West Virginia Representative David McKinley. Rep. McKinley has a long history of climate denial. Last fall, he got himself embroiled with scientists over whether increased carbon dioxide in the atmosphere increases global temperatures or not, passing himself off as an expert on the issue. You may have had the same thought I did when you saw that Congressman McKinley hails from West Virginia: "Of course! He comes from a state whose entire economy revolves coal." It is not hard to connect the dots between a once powerful industry afraid of disappearing and McKinley's climate denialism.

Some people may not alter their habits or reduce their carbon footprint because they do not comprehend the severity of this long-term, long-range threat and the part they play in that threat. For others - including businesses, it is simply about money. Their virulent, relentless attacks on sound science - science that has been settled for a considerable length of time - is because they don't want to lose money. Individuals like Representative McKinley are in the pocket of these fossil fuel industries, pushing their pseudo-science and denialist drivel to get the money the industry showers over them for campaign or other pet projects they want funded.

McKinley's disregard for the environment is clear. Every time a destructive coal-mining/fossil fuel practice or byproduct is being legislated against, Mr. McKinley always sides with the fossil fuel industry. Congressman McKinley is of the opinion that there is still a debate going on about climate change. His latest action, in regard to the amendment he proposed adding to the Military Budget, shows a man who is reacting to the mainstream acceptance of climate change as fact. He has the industry's back, but not the actual humans who make up his constituency. This is the problem with irrational people who wield power. Fact and reason may surround them, but they can still whip up enough frenzied support to control the direction we take on the environment through the purse strings. We can rejoice that many more are actually convinced of the science both professionally and on an individual level, but we must remain vigilant against those who continue to put forth fiction and flawed policy based on that fiction.

Our Brains vs. Environmental Challenges

This morning I was listening to the Climate One podcast that I regularly follow and found the topic very interesting. It looks at why we as humans are slow to respond the mounting evidence that our planet is undergoing chaotic climate change because of our activities. The discussion between three different authors on what was termed "Ecological Intelligence" explored ways we can change our brain habits and moral thinking in to understanding and acting on the facts we have on the threats posed to us from chaotic climate change.
  
The topics I have written about so far on this blog show how varied and complex the threats are from our impacts on the climate and the environment. It can be hard to process, with the mind only wanting to focus on a single issue. Despite our brain habits, climate change and ecological change are still complex, interconnected issues. Our decisions now will have significant ramifications down the line for future generations of humanity. It is therefore vital that we start seeing the challenges for what they are. Our intellect and innovation may be strong, but we still have to train our brain to deal with the facts so we can use our intellect and innovation in the correct way.

I have provided the link  above so that you may listen to the discussion on ecological intelligence as well. I encourage readers to follow the Climate One podcasts because they cover a range of environmental issues and host some great experts on these issues.

What Does It All Mean, Doctor?

My partner asked me last week if I had heard the news that scientists discovered that the ice in Antarctica was melting and would be completely gone in the next few centuries. I remarked that I had seen a headline that had mentioned the Antarctic and sea-level rise, but I didn't read the article due to time restraints. In the days following that initial discussion with my partner, the story about this research has been everywhere. And for good reason.

Sea-level rise is one of the biggest threats humans face from a warming planet. As I learned in my Coastal Environments class more than a year ago, we are already experiencing sea-level rise. This is why coastal storms such as Sandy and the winter storms which battered the British coast this year were so devastating. Sea barriers that had been built to withstand 1 in 100 or 1 in 500 year storms were easily overtopped because the sea-level was higher than when these defenses were built (most "modern" sea defenses were built 50 - 100 years ago). In my class, we discussed how the IPCC 2007 report predicted a 0.6 to 1.9 feet rise in current sea-level by 2100 (The most recent report put sea-level at 1.7 to 3.2 feet higher than current levels by 2100). This prediction did not take into account ice melt from the great Antarctic ice sheets, but rather was derived from a combination of glacier melt (including some major glaciers in Greenland) and expanding water due to warmer sea temperatures. Of course, we all discussed the possible scenarios if Antarctica melted. It wasn't good, but since the scientific research had not yet provided any direction on the plausibility of this scenario, it wasn't entertained for long.

However, this week humans did get some definitive scientific research on this scenario. Forty years of careful research, monitoring, and analysis have led a team of scientists to conclude that the West Antarctic is on an unstoppable path to losing its land ice. They said their research has indicated that it will be slow at first but in the next 200 to 500 years, it will suddenly jump into high gear leading to a sea-levels at least 12 feet higher in addition to what has already been projected by climate scientists. Another, less-talked about study found that an ice basin in East Antarctica was also destabilizing, but the time-scale for that was much longer 5,000 to 10,000 years.

So what does this all mean for us? For starters, two-thirds of the world's population live in coastal areas, so the impact of sea-level rise is a clear and present danger. Even the meager 1.7 to 3.2 feet rise will cause havoc with infrastructure, buildings, communities, and agriculture in all areas of the world. Some island nations face obliteration based on the current IPCC prediction. This new study on the West Antarctic ice sheets has brought this very serious challenge back into public consciousness. It presents a litany of problems and questions such as: where will all the people go? how long will it take governments to come up with "managed retreat" plans to avoid mass refugee events? how big will the fight be between property owners and government if a "retreat" plan is implemented? will we wait to the last minute to confront this crisis as well?

Of course, this study is just the first one. More will come and need to be carried out. But the fact that 40 years of monitoring went into this study gives it a lot of weight. That is a lot of evidence that has built up. What does it all mean? Perhaps it is that we really have to address the fact that we are a part of this planet. We can innovate, we can engineer, but ultimately the human race is subject to the same forces that all other species are. It means that there will be more haggling and debate in the 200 years about whether the science is real, and who will get the pay out. It means a drastically different world beyond a chaotic climate. I am confident that humans will do something about this, however, it is really clear that our glutinous consumption of fossil fuels in the 20th and early 21st centuries will alter how our posterity will live for centuries to come.

Nature Found a Way

Yesterday's post showed that we humans can actually redeem ecosystems from our environmental sins. Along that same vein, The New York Times published an article today about how biological life is adapting to the extreme conditions that the region around Chernobyl was exposed to. The 1986 nuclear power plant disaster spewed very high amounts of radiation into the local atmosphere that spread globally. However, much of that radiation fell back to the ground, contaminating the surrounding region. This had serious impacts on the flora and fauna in the area, including the death of forests. For reasons of public safety, an exclusion zone extending out 18.6 miles in all directions from the power plant was set up, preventing people from living in the 1,000 square mile area for at least 50 years.

Ongoing scientific research on the mass radiation event's effect on the surrounding environment has yielded interesting results. As the article and various other studies have pointed out, while biological life did suffer in the immediate aftermath of the explosion, it has done extremely well since. It has even provided unique insight into adaptation and selective events which put pressure on different species. The article in the Times is well worth the read and provides a unique glimpse into the resiliency of nature. It may suffer horrendous blows, but somehow life finds a way to survive, though not always the same as it was before. It will be very interesting to see how nature has "reclaimed" and progressed throughout the exclusion zone since humans don't have a chance to incorporate land management plans here.

Redemption

To celebrate my newly acquired position as an environmental monitor at Freshkills here in New York City, I thought I would inform myself and others about the place that used to be a human-made atrocity. Freshkills is located on the western edge of Staten Island. From 1947 to 2001, it served as New York City's municipal dumping ground. It infamously became the world's largest landfill and some argued it's piles of rubbish were getting so high they would be taller than most mountains along the eastern seaboard. Important wetlands gave way to stench and pollution.

All of that has changed now. Since its closure in 2001, a grand reclamation project has been underway to turn the area into a network of woodlands, wetlands, and other green spaces. The public park is now the largest in New York City, three times the size of Central Park. The entire reclamation project will not be completed until 2030, but it is already showing how we can undo a lot of the problems we have created. Reseeding native plants and planting flora in experimental ways is providing ecologists and land managers a glimpse into how urban ecological restoration takes place. During Superstorm Sandy, the wetlands in Freshkills absorbed a lot of surge, just as they would have in a "natural" setting, resulting in diminished storm damage on the western side of Staten Island.

The methane created by the decomposition of the waste has been harvested and put to use as an energy source. Native fauna are returning to the area, replacing the vast flocks of seagulls trying to eat our garbage. The water is less polluted now than it has been in years. While Freshkills has a way to go yet - and it will never be what is was before it became a landfill - it stands as a testament that society can right the environmental wrongs we inflict. It takes innovation, it takes leadership, it takes risk, but it can be done. I am excited to be a part of this project and to carry out environmental research in the park.

It's Complicated . . . Part 2

A few weeks ago, I wrote about the complicated nature of invasive species. I mentioned some of my studies at the University of Liverpool helped me to understand the complexity that exists between native and non-native species and the management plans that we as humans have developed. Today I decided to post a short essay I wrote on this particular subject while attending University. For my American readers, since my school of higher learning was in the UK, some of the phrases or spelling may seem wrong, but are in fact correct within Britain. Links will be provided to describe unfamiliar scientific words and scientific papers for those who want to research the topic. I hope you enjoy and gain a deeper understanding of the invasive species debate.

The Importance of Considering Non-native Species When Making

Conservation Management Decisions

Introduction 

Biodiversity loss is becoming a major concern in present-day ecological, cultural, and economic

circles. The loss of biological diversity within ecosystems is attributed to many different factors

and management regimes must take these factors into account to find success in conservation.

One of the top 5 factors of biodiversity loss in the United Kingdom and the United States (U.S.)

is attributed to invasive, non-native species (EPA, 2012; Natural England, 2013). Non-native

species that move into an ecosystem can cause widespread changes that significantly impact

biodiversity. 

Exotic species have the potential to change predator-prey relationships, out-compete native 

species, change ecosystem regimes, and impact agricultural and historic culturally important

species (Schlaepfer et al, 2011:429). Many conservation managers see all invasive, non-native

species as a negative intrusion on local ecosystems and set goals of complete removal

(Shackelford et al, 2013:55). Though many non-native species do impact systems in negative

ways, management schemes must take into account the complicated manner in which these

species interact with their new environment. In this essay I will explore the importance of

understanding interactions between non-native species and their new habitat in order to develop

management techniques that address the complex nature of the problem. I will first examine

cheatgrass invasion in the Great Basin of the western U.S. and how managers are learning the

multifaceted issues in preventing its spread. Next, I will investigate the unique interactions of 

tamarisk plants with local species in the western U.S. and how that may affect conservation and 

management plans. 

Cheatgrass 

Cheatgrass, Bromus tectorum, has become a major invasive, non-native species in the Great

Basin. First introduced to the U.S. in the 1890s through wheat supplies, it has established itself as

an opportunistic plant of the dry, high deserts of the Great Basin region (Pellant, 1996:1). Its

spread has been exacerbated due to heavy grazing by domestic animals and fire disturbance

(Fuhrman et al, 2009:2; Pellant, 1996:1). B. tectorum is an annual grass that is able to out-

compete many native species by growing and germinating earlier than other annual and perennial

grasses (Goergen et al, 2011:2). The grass completes its lifecycle quickly and then dies back,

making it a prime fuel source for wildfires (Balch et al, 2012:174). Because the grass is opportunistic, it has made its home in several different ecosystems including halophytic shrublands, sagebrush steppe, pinyon-juniper stands, and even ponderosa pine stands just outside the Great Basin (Balch et al, 2012:174; Furhman et al, 2009:2). Its vulnerability to fire has increased fire returns in all of these regions. Ecosystems that have seen B. tectorum become established have had fire returns reduced by half than those parts where cheatgrass is not growing (Balch et al, 2012:178). Fires in cheatgrass regions are more likely to burn larger areas and for longer periods (Balch et al:178-179). Increased fire returns threaten whole ecosystems with regime change from woody plants to herbaceous ones, especially in sagebrush steppes which are quite sensitive to fire (Balch et al:178-179; Furhman et al, 2009:2). 

Zion National Park in southwest Utah has prescribed burns from time to time to help manage the 

ecosystems within its boundaries (Fuhrman et al, 2009:1). Though fire was suppressed in the

U.S. for many decades, its usefulness to ecosystems is now understood (Fuhrman et al, 2009:1). 

However, managers have found that cheatgrass is establishing itself in areas disturbed by fires,

especially in areas where fire has historically been supressed (Fuhrman et al, 2009:3-4). This has

the reverse effect that managers are looking for when prescribing burns – reduction in easy fuel

sources (Fuhrman et al, 2009:4). Conservation managers have concluded in this particular case

that because cheatgrass interrupts a return to historical fire schedules, control of this invasive

species should not include burning (Fuhrman et al, 2009:4). 

 

Although fire is not a good control for this exotic species, some researchers have found that there 

may be other ways to combat its spread and help valuable ecosystem species retake their

dominance. For example, in sagebrush steppes the limiting factor of restoration is the re-

establishment of native grasses (Ray-Mukherjee et al, 2011:359). Research by Ray-Mukherjee et

al found that one of the characteristics that make B. tectorum so successful is its focus on

establishing a large root network to help the plant access constrained resources (Ray-Mukherjee

et al, 2011:363). When compared with native grasses, it was found that indigenous Snake River

wheatgrass, Elymus wawawaiensis, has similar characteristics which could make it a good local

competitor of cheatgrass (Ray-Mukherjee et al, 2011:364-365). 

 

Likewise, Goergen et al studied the effects of cheatgrass on native annual and perennial grasses. 

Their research revealed that native grass populations which had been invaded by B. tectorum

were responding phenologically to help them compete (Goergen et al, 2011:4). The growth and

flowering of the native grasses occurred earlier in communities with cheatgrass than

communities without it, which allowed many of these systems to be more tolerant of cheatgrass

competition (Goergen et al, 2011:5-6). What is clear from this research is that native grasses

found in colonised areas may actually act as resource material in restoration efforts (Goergen et

al, 2011:7). 

 

Conservation managers must account for the dynamism of communities to an exotic species such 

as cheatgrass, as well as for its habits when implementing controls. B. tectorum increases fire

return and establishes itself after an area is burned. Other native plants have responded by

starting growth and flowering earlier than they would otherwise. Some control may be

implemented by seeding areas with competitive native grass. The effects of fire, earlier

phenological responses, and competitive native species require management of cheatgrass which

will not result in overall harm to native plant populations if indigenous species are to be

protected from substantial biodiversity loss. 

Tamarisk 

Tamarisk (Tamarix spp.), or saltcedar, is another plant which has moved into the western U.S. 

and outcompeted native trees and large shrubs. It has become a dominant plant in riparian

communities and is thought to be negatively impacting water availability, biodiversity, and

overall habitat quality (Hultine et al, 2010:467). Many ecologists and land managers have

previously taken an approach that aggressively removes tamarisk through various means. This

has included chemical spraying and the release of the parasitic tamarisk beetle (Hultine et al,

2010:467; Paxton et al, 2011:255). These tactics were undertaken before understanding how

native plant and animal species were responding to the exotic saltcedar (Belote et al, 2010:449-

450; Shackelford et al, 2013:58-59). 

 

Recent studies are establishing the complex nature of tamarisk and local, native species.

Tamarisk is thought to alter soil salinity and out-compete similar plants for the limited water

supply, which in turn has led conservationists to believe there has been a reduction in

biodiversity in areas dominated by this plant (Belote et al, 2010:450). Whilst there has been an

overall reduction in native trees such as cottonwood, willows, and box elder in riparian zones,

many other species have adapted to the monotypic stands of saltcedar (Paxton et al, 2011:255-

256). For instance, the endangered SouthwesternWillow Flycatcher nests in tamarisk trees and

depends on the shade they provide to successfully reproduce and rear their young (Hultine et al,

2010:471; Shackelford et al, 2013:58). Many other native and migrant birds rest in and feed on

insects found on tamarisk (Hultine et al, 2010:471; Paxton et al, 2011:256-261). The danger for

these birds, especially for the endangered Flycatcher, is that the parasitic beetle defoliates 

the tamarisk in late spring over successive years until the plant eventually dies (Paxton et al,

2011:256-261). This makes Flycatcher eggs vulnerable to excessive heat and reduces insect

numbers for other insectivorous birds (Paxton et al, 2011:256-261). 

 

Birds may have other woody plant species they can nest in and feed off of; however, their ratio is 

small, increasing pressure on all bird species (Hultine et al, 2010:471). A study in Grand Canyon

National Park also found that saltcedar stands had similar species richness to non-invaded areas;

in fact, richness and diversity was higher because there were many other non-native species

found in tamarisk stands (Belote et al, 2010:453). In addition, areas where tamarisk was

proactively removed did not undergo a return to native plants over 1-3 years after removal

(Belote et al, 2010:455). These results suggest that either native species are in such low numbers

that proactive seeding and planting must take place to help revive the native tree populations, or

that tamarisk has already altered the soil salinity, making it difficult for native populations to

recover their historic spread (Belote et al, 2010:456-457). 

 

Finally, research has found that tamarisk has actually contributed to the stabilising of river and 

stream banks, as well as making the flow of the channels narrower and deeper (Hultine et al,

2010:469). This has caused a change in sediment supply and flooding patterns that native tree

populations have historically relied on (Hultine et al, 2010:469). Control and removal of

saltcedar will most likely change flooding patterns again, resulting in significant erosion during a

flood event because of the narrower, deeper flow of water channels (Hultine et al, 2010:469).

Such a scenario has the potential to impact ecosystems downstream, as well as hindering the

ability of native plant populations to move in and keep the banks stable. 

 

Tamarisk is indeed an exotic, invasive species which has already altered arid riparian ecosystems 

in the western U.S. Native populations of riparian woody plants may have declined, yet many

species of plants and animals have adapted to the changes. Aggressive control techniques have

the potential to disrupt or extirpate species which have adapted to use the tamarisk stands for

their own benefit. In addition, because saltcedar stands are found to harbour other invasive

species, the removal of tamarisk opens up the possibility of invasion by another exotic species,

without the return of large native plant populations (Hultine et al, 2010:470-471). Again, it is

important for conservationists and land managers to consider the implications of control

measures in regards to non-native species, as they may actually negatively impact biodiversity. 

Conclusion 

Non-native species that are introduced into a new location can have very negative influences on 

native species and the overall health of an ecosystem. However, as I have explained in this essay,

non-native species interact with the ecosystem in very complex ways. Controlling or removing

the spread of an exotic species must be undertaken only when these interactions are understood.

If the interactions are not fully understood by managers, attempts to extract an exotic species

from a habitat may actually contribute to its spread, such as fire and cheatgrass. Other times, it

may actually result in threatening many other endemic species which have come to rely on the

invading plant, as is the case with the Flycatcher and tamarisk. In order to preserve native

biodiversity, careful steps and consideration need to be taken when addressing non-native

species. 

References

Balch, J.K., Bradley, B.A., D’Antonio, C.M.,Gómez-Dans, J., 2013. Introduced annual grass 

increases regional fire activity across the arid western USA (1980-2009). Global Change   Biology  19, 173–183. 

Belote, R.T., Makarick, L.J., Kearsley, M.J.C.,Lauver, C.L., 2010. Tamarisk Removal in Grand 

Canyon National Park: Changing the Native - Non-native Relationship as a Restoration Goal. 

Ecological Restoration 28, 449–459. 

Environmental Protection Agency, 2012. Invasive Species. Water: Habitat Protection. 

http://water.epa.gov/type/oceb/habitat/invasive_species_index.cfm. Accessed 5 March 2013. 

Fuhrmann, K., Decker, C., Johnson, K.A., 2009. Prescribed fire and nonnative plant spread in Zion 

National Park. Park Science 26, 1–8. 

Goergen, E.M., Leger, E.A., Espeland, E.K., 2011. Native Perennial Grasses Show Evolutionary 

Response to Bromus tectorum (Cheatgrass) Invasion. PLoS One 6, 1–8. 

Hultine, K.R., Belnap, J., Van Riper, C., Ehleringer, J.R., Dennison, P.E., Lee, M.E., Nagler, P.L., 

Snyder, K.A., Uselman, S.M.,West, J.B., 2010. Tamarisk biocontrol in the western United 

States: ecological and societal implications. Frontiers in Ecology and the Environment 8, 467–474. 

Natural England, 2013. Non-native species. Our Work. 

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Paxton, E.H., Theimer, T.C., Sogge, M.K., 2011. Tamarisk Biocontrol using Tamarisk Beetles: 

Potential Consequences for Riparian Birds in the Southwestern United States. The Condor 113, 255–265. 

Pellant, M., 1996. Cheatgrass: The Invader That Won The West. Bureau of Land Management. 22p. 

Ray-Mukherjee, J., Jones, T.A., Adler, P.B., Monaco,T.A., 2011. Immature Seedling Growth of Two 

North American Native Perennial Bunchgrasses and the Invasive Grass Bromus tectorum. 

Rangeland Ecology & Management 64, 358–365. 

Schlaepfer, M.A., Sax, D.F., Olden, J.D., 2011. The Potential Conservation Value of Non-Native 

Species. Conservation Biology  25, 428-437. 

Shackelford, N., Hobbs, R.J., Heller, N.E., Hallett,L.M., Seastedt, T.R., 2013. Finding a middle-

ground: The native/non-native debate. Biological Conservation 158, 55–62.