Monthly Archives: May 2015

The Green Wall of……Grazers?!

Desertification is a process of land degradation whereby environments become increasingly arid and loose productivity over time [2]. Desertification occurs when land surfaces are transformed by human activities, including overgrazing, deforestation, surface land mining, and poor irrigation techniques. Desertification in the Sahel region of Africa is mainly attributed to an increase in human activity and their grazing livestock.

For a long time it was thought that the major factor causing desertification was the over grazing of livestock. This led to strict land use policies and a shift from livestock and wildlife coexisting on the landscape to a complete separation in an attempt to curb the effects of desertification. Wildlife became increasingly concentrated on nature reserves and due to land fragmentation, livestock was held on smaller land plots [4]. Yet it seemed as though the land began to get drier each year with less and less vegetation returning.

As the seriousness of desertification began to reach a global stage, many suggestions have been made as to how to stop such a process. One idea is to grow a wall of trees that stretches across the entire southern boundary of the Sahara desert, known as the Great Green Wall [3]. The idea being that setting up a natural barrier to desertification would reduce wind speed, stabilize the soil and increase soil humidity, halting or even reversing the process. Mainly due to a lack of global support as well as little local representation, the Great Green Wall has been a slow process. This initiative has also been contested as it could lead to unforeseen problems down the road. Concerns regarding water use are most often cited; the Sahel region is an arid landscape and there may not be enough water to grow such a large wall of trees [3].

If restricting grazing only makes things worse and no one is willing to spearhead a large intervention event such as the Great Green Wall, what can be done? One solution that has been proposed is to not restrict grazing but rather release it. Using livestock to mimic the grazing behaviors once carried out by native herds, which have since been reduced due to human encroachment and land fragmentation, would encourage natural turnover of grasslands and sustain a healthy environment [1]. How does this happen? Desertification occurring in arid lands sees seasonal changes in the environment with a hot dry season and a wet growing season. Grass grows really fast during the wet season, but as things become drier the plant biomass above ground dies. These dead plants need to decay biologically and quickly so that new plants can grow during the next season. However, when large herds of grazers are absent, the dead material shifts from rapid biological decay to gradual breakdown through oxidation and weathering. This leads to dead plant material blocking light from reaching the soil and prevents new plant growth. If there is enough rain, grasslands shift to shrubs and trees, but when rainwater is scarce, they shift to bare, generally algae-covered soil and small woody bushes. As space between plants increases, the effectiveness of rainfall decreases. Rain that soaks into the soil evaporates back out. Or, in the case of extreme rain, most of the water runs off, causing flooding. Using large herds in combination with planned grazing patterns to mimic natural cycles will eventually start to restore the land and allow for it to become self-sustaining.

 

-Scott Morton

 

 

Works Cited:

  1. Savory, Allan (1983). The Savory Grazing Method or Holistic Resource Management. Rangelands. 5(4)
  2. http://earthobservatory.nasa.gov/Features/Desertification/
  3. O’Connor, D. and Ford, J. (2014). Increasing the Effectiveness of the “Great Green Wall” as an Adaptation to the Effects of Climate Change and Desertification in the Sahel. Sustainability. 6:7142-7154.
  4. Hobbs et al. (2008). Fragmentation of rangelands: Implications for humans, animals, and landscapes. Global Environmental Change-Human and Policy Dimensions. 18: 776-785.

 

 

The Lead Stops Here

The use of lead shot for hunting and sport shooting has caused major problems for upland foraging birds (Raptors). Raptors are predatory birds that use their feet and talons to catch and kill their prey. Recently, I started volunteering at the Rocky Mountain Raptor Program (RMRP), which is a non-profit organization that provides medical care and rehabilitation to these birds. In a two month period I witnessed three Raptors who were brought to our facility suffering from lead poisoning, of which only one survived and was able to be released after undergoing extensive chelation treatment. After seeing the effect of lead first hand, I wanted to know more about how these birds were becoming poisoned and how can we prevent this from happening in the future.

Animals can be exposed to lead in many ways: mines, smelting plants, harbors, industrial areas, urban areas and leaded petrol combustion [3]. Hunting with lead shot is the primary cause of lead toxicity in raptors due to their foraging behavior. Raptors are obligate carnivores who are able to get all of their water and nutrients from meat. They also exhibit generalist and opportunistic feeding behavior so when they see a gut pile left behind by a hunter they will take full advantage of this tasty treat. This type of foraging behavior causes raptors to inevitably ingest lead that is left behind in gut piles, lost or un-retrieved game, and when capturing wounded animals who have shot embedded in their tissues [2]. Once in the system the lead is rapidly dissolved by the low pH of the stomach and absorbed into the bloodstream [4]. Lead accumulates in the kidneys, liver, brain and most of all in the bones due to its long biological half-life. Lead also has the ability to disguise itself as other metals and be taken up into the cells more readily. Lead disrupts important biological processes such as DNA transcription and enzymatic pathways [1]. High accumulation of lead in  bone is a result of exposure to low concentrations over long periods of time, which can cause mineralization of the bones in adult birds [5].

Symptoms of lead poisoning can be seen immediately in raptors and include distension of the proventriculus, green watery feces, weight loss, anemia and drooping posture [4]. It can also affect the nervous system and become detrimental to biochemical functions causing blindness, depression of certain blood enzymes, reduced reproduction, and impaired immune function [4]. Furthermore, it can result in behavioral changes that make raptors prone to predation, which results in higher mortality rates [4]. This is of direct conservation concern because many raptors are long-lived, slow breeding species with small populations like the California condor. In a study done by Clark and Scheuhammer on lead poisoning in upland foraging birds in Canada, four deaths of reintroduced California condors were directly attributed to leftover lead shot in deer carcasses [3].

Size, age, and proximity to human activity have monumental influences on the distribution of lead in a bird’s tissue. The bigger the bird the more energy it needs to take in and, therefore, they ingest large amounts of meat, which gives them a higher probability of ingesting lead than smaller raptors [3]. Figure 1 on the left is taken from a study done on lead exposure in four different raptor species from Spain [3]. It shows that lead concentrations have a direct correlation to the size of the bird, which are listed as follows from largest to smallest; Eagle Owl > Buzzard > Kestrel > Little Owl. The reason for the low concentrations found in the buzzard compared to its size, as opposed to the smaller two raptors, can be attributed to the fact that the European buzzard inhabits places with low human activity.

Hunting season also plays a factor in lead exposure in large birds of prey [1]. Human activity is the main source of environmental lead and is why these birds are becoming poisoned; the closer raptors are to human activity (hunting, sport shooting, etc.) the higher the lead concentrations found in the bloodstream [4]. With the human population growing at an exponential rate, small towns will expand into urban and industrial areas. This will increase human contact with wildlife populations which, in turn will increase raptor exposure to lead shot.

Lead has been shown to cause long term detrimental effects on humans and mammals [5]. It is a highly toxic heavy metal that can be released into the environment in many ways. Acute exposure (high concentrations over short time) in vertebrates can lead to death, while chronic exposure can affect reproductive success, behavior, physiological and immune responses [5]. Lead may be a cheaper alternative for ammunition but the effects it has on wildlife is very expensive. It’s not just raptors that are of concern here, other species of birds have also been known to suffer from lead poisoning due to lead shot left behind from sport shooting or hunting. These species of birds mistakenly pick up lead pellets along with grit for their gizzards. This has been seen in species like whooping cranes, sandhill cranes, Virginia rails and even a wild turkey [4]. In 1991, the use of lead shot on waterfowl was made illegal in the United States. Since then, alternative forms of non-toxic shot have been introduced and approved for waterfowl that can also be used on upland game [4].

The most obvious solution for this growing problem would be to ban the use of lead bullets and replace them with a form of non-toxic pellets. We could also follow the lead of Britain, Australia, Sweden, Denmark, Norway, Finland and the Netherlands in establishing restrictions on the use of lead for hunting. Lead free zones can be established in places like breeding grounds and migratory rest stops that are important to wildlife. All of these alternatives are feasible and can be implemented with very little repercussion to us. For the future of our raptors and other bird species, something needs to be done soon before it is too late.

Works Cited:

[1] Clark, A. J., and A. M. Scherhammer. “Lead Poisoning in Upland-foraging Birds of Prey in Canada.” Ecotoxicology 4th ser. 12.1 (2003): 23-30. Web of Science. Web. 20 Mar. 2015.

[2] Custer, Thomas W., J. Christian Franson, and Oliver H. Pattee. “Tissue Lead Distribution and Hematologic Effects In American Kestrels (Falco Sparverius L.) Fed Biologically Incorporated Lead.” Journal of Wildlife Diseases 20.1 (1984): 39-43. Web of Science. Web. 20 Mar. 2015.

[3] Fisher, Ian J., Deborah J. Pain, and Vernon G. Thomas. “A Review of Lead Poisoning from Ammunition Sources in Terrestrial Birds.” Biological Conservation 131.3 (2006): 421-32. Web of Science. Web. 20 Mar. 2015.

[4] Gangoso, Laura, Pedro Álvarez-Lloret, Alejandro. A.B. Rodríguez-Navarro, Rafael Mateo, Fernando Hiraldo, and José Antonio Donázar. “Long-term Effects of Lead Poisoning on Bone Mineralization in Vultures Exposed to Ammunition Sources.” Environmental Pollution 157.2 (2009): 569-74. Web of Science. Web. 20 Mar. 2015.

[5] García-Fernández, A. J., M. Motas-Guzmán, I. Navas, P. María-Mojica, A. Luna, and J. A. Sánchez-García. “Environmental Exposure and Distribution of Lead in Four Species of Raptors in Southeastern Spain.” Archives of Environmental Contamination and Toxicology 33.1 (1997): 76-82. Web of Science. Web. 20 Mar. 2015.

 

Derwent Estuary, the Finest Sea Star Hotel

The world thrives on life’s diversity. Every natural space or ecosystem is filled with a variety of organisms that together work to keep the earth in its natural cycle. This natural cycle is rather delicate, and if parts of the puzzle are absent, the whole system does not work as well. One example of this is when a pivotal or keystone species is taken out of an ecosystem (by extinction for instance) and alters the ecosystem by disrupting the food web or natural order of the habitat. Species can be eliminated by natural and unnatural causes. Some unnatural causes include urbanization, human disturbances, hunting and poaching, and invasive species inhabitation.

Invasive species can come about as a result of human disturbance activity. These disturbance activities include people picking up and moving species to a different place, or animals attaching themselves to transportation vessels and traveling large distances, ending up in an environment they are not native to. One example of this is found in the Derwent Estuary in Tasmania, where millions of Northern-Pacific sea stars have moved into and overtaken the waterway. These sea stars are native to Northern Pacific areas such as Japan, and because ocean currents do not naturally carry them down to Australia, it is thought that some sea stars in larval stages were sucked up and carried by harboring ships to the Tasmanian shores, thus they are classified as an invasive species [1].

In a study published in The Journal of Applied Ecology, it was found that the feeding and breeding habits of these sea stars make them particularly successful in the Derwent Estuary [1]. The Northern-Pacific sea stars feed on bivalves (clams, mussels, scallops, etc.) and reproduce by external fertilization (expelling sperm and eggs out into the water to be fertilized). Due to the Derwent Estuary having an abundance of manmade docks, jetties and piers in the water, there is plenty of available substrate for bivalves to latch on to and filter feed. This provides the sea stars with an abundance of food in a very concentrated area. Not only do they thrive on the food source, but also the close vicinity of the docks provides a convenient space for the sea stars to expel their eggs and sperm into the water to be readily fertilized by other sea stars in the area. The overabundance of sea stars in their non-native environment significantly depletes the native species (assortment of bivalves) that are typically found there. In this way, the human construction of docking structures has facilitated an explosion of this invasive species population, and significantly decreased biodiversity.

With our knowledge of the causes and consequences of this problem, we have the opportunity to solve it. One approach would be reducing the availability of the food source for the sea stars by either displacing or blocking off the mussels and clams attached to docking areas. This could be done by fencing off the docking substrate (after the bivalves have established themselves) so the sea stars can’t reach the bivalves. Another potential solution would be changing the structure of the docks so that they are non-attachable for sea stars, or so they are more spread out, making external fertilization less effective to slow their reproduction. Another approach being tested is the implication of ciliates that parasitize the male gonads. Introducing these parasites may be effective in controlling the reproductive rates of the invasive sea stars. Research would have to be done to ensure that the ciliate species is specific to the targeted invasive species and would not be detrimental to other species in the ecosystem.

Basically any method to decrease the numbers of sea stars will help to keep the bivalve populations at normal levels and sustain the biodiversity in the ecosystem. It is very important for diversity to thrive in any ecosystem because, if the natural order of things is thrown off, it is very hard to recover it by natural or artificial means. Halting the cause of what sparks invasive species populations can help control them before they get bad, and ultimately help preserve biodiversity.

–Cristiana Falvo
[1] Ling, S. D., Johnson, C. R., Mundy, C. N., Morris, A. and Ross, D. J. (2012), Hotspots of exotic free-spawning sex: man-made environment facilitates success of an invasive seastar. Journal of Applied Ecology, 49: 733–741.

[2] Bouland, Catherine and Goggin, Louise. The ciliate Orchitophrya cf. stellarum and other parasites and commensals of the northern pacific seastar Asterias amurensis from Japan. International Journal for Parasitology, vol 27; p 1415-1418.

Can Human Hunters become a Natural Part of the Ecosystem?

Who doesn’t love nature?  The fresh air blowing through the trees, the sweet songs of birds and frogs, and the absolute feeling of being free.  The chance to see a female deer and its fawn excite even the most urbanized kid and seeing a real life equivalents of Chip and Dale chasing each other would make anyone laugh.  Those who have worked with or have been in nature know that when nature is in balance, things work out beautifully for both man and nature.

But nature is not entirely balanced these days.

Despite the pristine appearance of our natural areas, there is a problem happening within.  Deer and elk have been visiting the riparian areas (where land and water meet) of streams, rivers, and lakes more often than they had before and have been consuming more than their fair share of sapling trees.  Why is this all bad?  Well, with the deer and elk visiting the riparian areas more often, they are consuming the sodium-rich plants that are essential to control soil erosion.  Studies have shown that with this combination of less plant life and more soil erosion, the deer’s and elk’s actions are destroying habitats for fish and amphibians by making the waters murky with sediment.  These sediments negatively affect farms as well [3].  This also has negative effects on local bird populations by modifying their breeding patterns [6].  And what about the lack of sapling trees?  With the lack of sapling trees, there are less and less trees to replace the older trees when they die of age, disease, parasites, or wildfires.

Why has this happened?  Three words: Lack of predators.

While it no secret that predators are important in controlling the population size of prey species, they are also important for other components of the ecosystem as well.  Along with eating their prey, they also influence their prey’s behavior.  Studies in Yellowstone have shown that following the reintroduction of the wolves, local elk population’s modified their behavior whereby they visit the riparian areas less often [1, 10] and browse less on sapling trees [9].  This is likely because sources of water are a popular place for predators to hunt and their presence has kept the prey moving often, not staying in one location for an extended period of time.

So it seems that predators are a sort of silver bullet to this issue.  But there is a problem with using predators to control prey.

A good number of places that suffer these sorts of habitat disturbances as in areas where there is not enough room to support large predators or they are too close to urbanized areas.  There is no doubt that no one would want large predators reintroduced right in their back yards, especially if their children might become targets for the would-be predators.

So if not large predators, what is the alternative?

Human hunters.

I would propose incorporating human hunters into areas that are close to urban areas or are too small to support large predators but suffering with riparian area destruction due to browsing by local wildlife.  Human hunters not only control prey populations, but also manipulate their behavior in a similar way as larger predators.  There have been studies that have shown that human hunting can be an alternative to a predator stimuli [5].  Human hunting has influenced deer behavior enough to give deer appropriate flight responses [12], influenced their browsing behavior to allow tree regeneration [8], and even made them roam at greater distances [11].  I would propose that we shall allow hunters to hunt at specific locations (e.g. heavily-used riparian areas and areas where tree saplings are being over-browsed) to stimulate these sorts of fear responses and allow the ecosystem to recover while also allowing them to be safe in other areas that are in need of more deer activity.

This is a solution that I believe would help the environment and it would definitely get some support from the hunting community.  But I fear that it won’t get a great deal of support.

Why?

Public opinion.

We’ve all grown up with Disney’s Bambi and with the negative public perception and opinion of hunting [4].  With this and animal rights groups like PETA obviously against it, it would be either really hard or near impossible to have this plan gain traction.  How could we get over this obstacle?  How would you get people to properly understand that this is a conservation movement?  Through proper education.  Hopefully, through proper education, we can teach people that this sort of hunting movement is vitally important for the wildlife, their habitats, and their ecosystem.  Also, we may need to emphasize that human hunting of wildlife is safer in those areas than reintroducing large predators.  For this is safer for the people and the animals.

Some would say that hunting is not good for nature, but I say to that as Aldo Leopold once said, “A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise.”[7]

-Austin Major

Works References

  1. Beschta, Robert L., and William J. Ripple. “The role of large predators in maintaining riparian plant communities and river morphology.” Geomorphology 157 (2012): 88-98.
  2. Côté, Steeve D., et al. “Ecological impacts of deer overabundance.” Annual Review of Ecology, Evolution, and Systematics (2004): 113-147.
  3. Cooper, J. R., et al. “Riparian areas as filters for agricultural sediment.” Soil Science Society of America Journal 51.2 (1987): 416-420.
  4. Decker, Daniel J., and Tommy L. Brown. “How Animal Rightists View the” Wildlife Management: Hunting System”.” Wildlife Society Bulletin (1987): 599-602.
  5. Frid, Alejandro, and Lawrence M. Dill. “Human-caused disturbance stimuli as a form of predation risk.” Conservation Ecology 6.1 (2002): 11.
  6. Kauffman, J. Boone, and William C. Krueger. “Livestock impacts on riparian ecosystems and streamside management implications… a review.” Journal of range management (1984): 430-438.
  7. Leopold, Aldo. 1966. A Sand County Almanac: With Other Essays On Conservation from Round River. Oxford University Press. New York, NY. 269 p
  8. Martin, Jean-Louis, and Christophe Baltzinger. “Interaction among deer browsing, hunting, and tree regeneration.” Canadian Journal of Forest Research 32.7 (2002): 1254-1264.
  9. Ripple, William J., and Robert L. Beschta. “Restoring Yellowstone’s aspen with wolves.” Biological Conservation 138.3 (2007): 514-519.
  10. Ripple, William J., and Robert L. Beschta. “Wolves and the ecology of fear: can predation risk structure ecosystems?.” BioScience 54.8 (2004): 755-766.
  11. Root, Brian G., Erik K. Fritzell, and Norbert F. Giessman. “Effects of intensive hunting on white-tailed deer movement.” Wildlife Society Bulletin (1988): 145-151.
  12. Stankowich, Theodore. “Ungulate flight responses to human disturbance: a review and meta-analysis.” Biological Conservation 141.9 (2008): 2159-2173.
  13. Stromayer, Karl AK, and Robert J. Warren. “Are overabundant deer herds in the eastern United States creating alternate stable states in forest plant communities?.” Wildlife Society Bulletin (1997): 227-234.