The Cardinale paper begins by explaining the importance of biodiversity in our ecosystem. Biodiversity is the “variety of life, including variation among genes, species and functional traits.” Having biodiversity simply allows for more functions and services of the ecosystem to exist and benefit us humans and the environment that surrounds us. The authors then go onto state that humans are “dismantling the Earth’s ecosystems” by lessening biodiversity.       The authors list six explicit reasons why we need biodiversity in our ecosystems in order to maximize the potential benefits.

1. Less biodiversity = less efficiency of basic ecological functions (capture resources, produce biomass, decompose, etc.)

2. More biodiversity = more stability of ecosystem over time

3. Less biodiversity = greater acceleration of change of environment

4. More biodiversity = more productivity

5. Less diversity among trophic levels changes the ecosystem more radically than less diversity within trophic levels.

6. Less biodiversity can lead to extinction of organisms and can affect the functions of the ecosystem.

Simply looking at these consensus statements, one can agree that biodiversity plays a fairly major role in regulating the balance of these ecosystems. It gives a more than marginal benefit to the functions and services that an ecosystem provides and should be preserved.

There is decades of research that went into concluding some of the effects and concerns dealing with biodiversity loss, BEF, and BES. With most of the basic research done already, it allows for scientists to try and delve deeper and attempt to understand more about how humans are affecting the surrounding ecosystems. Learning more allows for people who don’t care as much about biodiversity, BEF and BES to create a cost benefit analysis in their heads to better understand. Normal folk can think if the marginal cost of maintaining biodiversity outweighs the marginal benefit that these ecosystems incur for our society. If more people feel that the benefit is higher then they can begin to take steps to mitigate any damages and ameliorate the situation as best as possible. The decades of research and research to come, play a large role in shaping the public opinion surrounding these concepts in order to protect nature and human society from biodiversity loss and the effects generated from it.

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Biodiversity’s Importance

The caption above the article is interesting in that it provides a perspective. This perspective is one in which Earth is a unique planet in that it is able to support life. But the caption goes on to reveal that theres more than just life as there is incredible diversity on this planet. The beauty of this is that in all of the earths complexities with all its living creatures and inhabitants, there is a web that connects all us. This theme has been common in our readings and this time it is no different. The article tackles how biodiversity loss can ultimately effect humanity.

Studies have shown that having great biodiversity provides efficiency of the use and breakdown of essential nutrients along with increasing stability of ecosystem functions. However, there is consensus in that marginal losses of biodiversity can create even bigger changes to an ecosystem. Since everything is connected, this can be attributed to a statement in that diverse communities are productive. Similar to Silliman’s paper on trophic cascades, consensus statement five and six essentially stresses the dangers of loss of diversity between trophic levels.

The article takes into consideration that many of the studies are questionable in their validity in that the biodiversity of earth cannot simply be replicated. Even so, trends have emerged, and valuable data has come out of it.

What I found amazing is that the significance of biodiversity has been recognized over twenty years ago and was an issue many agreed to address, yet here we are two decades later and while some biodiversity loss could be expected, the rate of loss was primarily increasing.

While it seems that we have accomplished little in terms of prevention, there has been a lot of groundwork put in place in terms of understanding. As Cardinale says, the next generation of research is going to be carried out in a way that will make use of all of the previous years findings and maintain biodiversity.

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Understanding Humanity’s Impact on Biodiversity

“Biodiversity loss and its impact on humanity” by Cardinale et al. focuses on how human actions impact the ecosystems and biodiversity. Furthermore, it investigates and questions how further studies can better serve policy and management initiatives, as well as provide better evidence of the biodiversity loss in order to “reduce our uncertainties” relating to it.

Cardinale discusses BEF (biodiversity-ecosystem functioning) and BES (biodiversity-ecosystem services) research, as well as their differences: “Research on BEF had developed a large body of experiments and mathematical theory describing how genetic, species and functional diversity of organisms control basic ecological processes in ecosystems,” while BES studies were “mostly correlative, conducted at the landscape scale and often focused on how major habitat modifications influenced ‘provisioning’ and ‘regulating’ services of ecosystems.”

Cardinale et. al do a great job at thoroughly explaining the main points made both by BEF and BES research. What the paper stresses is the importance of using the “foundations laid down” by this research for the past 20 years, in order to make it more relative and realistic in today’s terms. In order for people to understand the consequences of biodiversity loss, the BEF and BES research need to be linked up and integrated together; in a sense, the two fields will need to work more closely together in order to support one another’s findings.

Cardinale warns that the “need to explore more realistic scenarios of diversity change that reflect how human activities are altering biodiversity is now urgent.” Essentially, this idea is what I understood and took the most from reading this paper and the findings it discusses. For “regular” people, who have limited understanding of ecosystems and biodiversity, it is necessary to explain the background of the extensive research that has been done for the past two decades. After that, and after successful predictive models have been developed, the problem of changing ecosystem and biodiversity should be presented in manner that is policy-relevant so that necessary changes can take place. Another tool that could be used in order to better understand what loss of biodiversity means to us as humans, is to estimate the value of the services provided by ecosystems, which was discussed in previous papers that we read, as well. Although economists have tools to do so, Cardinale notes that we still do not have a good understanding of the marginal value of biodiversity in providing us with the services.

In conclusion, what we students can take from this paper is that gaining a better understanding of how our activities affect biodiversity of ecosystems is necessary in order to make a change and turn around the biodiversity loss that is sure to affect us as humans if something is not done about it.

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Bottom-Up? Think Again.

It all started at Sapelo Island, Georgia, a place that once was thought to provide the evidence to support the hypothesis that the marsh grass production is controlled by bottom-up forces. Now, due to the experimentation done by Silliman and Bertness at the the turn of the century, we find these facts to be flipped. It is odd to think that for so long we could be wrong about this. No one dared to challenge the bottom-up theory; it simply became a widely accepted fact that primary producers controlled salt marsh cordgrass production. What I wonder is what were the conditions and methods of the experiment done prior to Silliman and Bertness’? Were there drastic errors involved and how did they prove their hypothesis of bottom-up control?

In any case, it was very strategic for Silliman and Bertness to conduct their experiment in the very location that this bottom-up theory was produced. Using the same natural environment to conduct their 2 year long experiment on Littoraria irrorata (periwinkle snail), what they graze on (cordgrass), and who their predators (blue crabs). The results they found were shocking. The fact that in the controlled environments without predation, grazing snails took one of the most productive grassland systems in the world and turned it to a barren mudflat in only 8 months, is insane. Now take this idea and apply it to all the grassland systems, unimaginable but could become a reality. As Silliman proves, if there are no predators left to eat the grazers in these ecosystems, all of the biomass will be lost.

A key quote I found that I feel exemplifies the purpose of this study is, “Understanding how marshes respond to such perturbations is key to the survival of these ecologically and economically important habitats.” Humans must realize that the resources are not infinite. Everything we do has repercussions, and the Earth can only give so much.

Where do we go from here? Since the publication date of Silliman paper, is there anything in action to protect the Blue Crabs? One would hope there are laws in place limiting the amount of Callinectes sapidus taken from the marshes so we can protect Blue Crabs from being over-fished, and thus causing these precious ecosystems to stay intact rather than be flattened to mud pits.

It seems Silliman forgot to include the top most level of the top-down control hierarchy in Figure 2. Us.

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The implications of our Top-Down Systems

The Silliman and Bertness article shows the importance of the trophic cascade. The authors essentially talk about how although a bottom-up approach of nutrients in a system can have an effect on an ecosystem, the main method of regulation is the delicate balance and hierarchy of the food web, with the most important players being the predators in an ecosystem. So they figured this out by creating five experimental situations with different concentrations of a snail species (Periwinkle) feeding on a primary producer called Spartina. The reason that they had these different concentrations was to essentially emulate how the populations of the snail would be with or without predators; with the higher concentration of Periwinkle indicating an absence of predators, and the lower ones a presence of predators. The experiments showed that at high densities the Spartina got eaten up to 88% greatly decreasing primary production and nutrient richness in the salt marsh.It was stated also that “grazing by snails at the same density transformed one of the most productive grassland systems in the world (up to3,700 g dry wt C per year; ref. 10) into a barren mudflat within8 months” which shows that not only does this have a major impact, but that it happens very quickly. The experiments with the lower snail concentration showed a better rate of primary production which essentially implies that an increase in predators essentially has an increase in primary production of an ecosystem.

The findings of Silliman and Bertness are very informative to scientists and any environmental decision makers because it shows us what the most impactful determinant of an environmental ecosystem is, which is the constant regulation of organisms through a trophic cascade. It was pretty surprising to me that these findings were submitted in 2002 which to me seems relatively new in the grand scheme of human ecological impact. At the end of the article it talks about how humans overfish certain areas and how this has detrimental impacts on the ecosystem because of our removal of natural predators. This got me thinking about how vast our human impact is on virtually every ecosystem in the world. And from a food stand point it raises a very interesting ethical question of buying “wild caught” fish as so called healthier options when perhaps these options are probably more detrimental to the natural environment. I also wonder if we are a necessary predator in some trophic cycles. By now we have established ourselves as predators at the top of the world food chain. So by Silliman and Bertness’s findings if we disappear or drop in population will this in fact be terrible for ecosystems around the world? Perhaps this wasn’t always the case, but maybe after we shoved ourselves at the top of these trophic levels maybe we in turn changed the populations and now are invariably involved in consuming these secondary consumers. I know for example, that hunters do a great job of maintaining and regulating deer populations and that there are times in the year when the population of game goes up and to keep it healthy we have to kill deer for the sake of the greater ecosystem. There are a host of questions that can be asked about these findings but without a doubt, Silliman and Bertness do make us question what our role is in the worlds many trophic levels should be.

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Bottom-Up or Top-Down?

Prior to reading Silliman and Bertness’ paper I thought that most ecosystems were bottom-up systems and that physical and chemical factors had the strongest influence on their organisms. After all, the nutrients an organism is exposed to, the environment it lives in, and the food it consumes all greatly affect how it reproduces, survives, and interacts with other species. I did not think that the consumers would have that big of an effect on the structure or function of an ecosystem. However, Silliman and Bertness’ paper proved the importance and influence of top-down controls on ecosystems and primary production, specifically in salt marshes, which are the most productive systems in the world.

Silliman and Bertness performed three different experiments to test out the effects of Littoraria and a trophic cascade on cordgrass production in salt marshes. Their experiment concluded that Littoraria had a strong top-down control of cordgrass production and that simple trophic cascades regulate the structure of southeast marshes. They also concluded that by eliminating predators, salt marshes could be converted into mudflats by plant-grazing snails.

Scientists and environmentalists have said for years that overfishing is a serious problem, but I did not fully grasp its gravity until I read this paper. By fishing for the bigger fish in the sea, which happen to be the consumers of their own ecosystem, we are in effect altering the food web, primary production system, and interactions amongst the other organisms. Not only do we affect the organisms, but the structure and physical traits of their environment as well. Consumers have such a strong influence on the structure of an ecosystem and by depleting the consumer population we can alter the whole ecosystem.

Silliman and Bertness’ findings made me realize once again that people have such a strong influence on the environment and that we should use this knowledge to better protect the earth. Although many people enjoy fishing for recreational or economic reasons, we should also be aware of how this simple activity can influence the structure and function of other ecosystems and its habitants. If salt marshes do turn into mudflats, it will not only harm the other fish and plants in the ecosystem, but humans as well. In a sense we have a symbiotic relationship with the environment and in order for us to be able to benefit from it, we have to do our part and take care of it as well.

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A New Approach

Up until now, I’ve associated ecosystems with a bottom up perspective-the physical and chemical factors in primary productions. Whether it be the amount of sunlight available to plants, the temperature of the ecosystem, or maybe the nutrients in the soil, I’ve generally removed the consumer for the equation of controlling plant growth. When we narrow the scope of our discussion to plant growth, I’ve always failed to realize a consumer’s impact. Perhaps I’ve seen pollution as a consumer influence,waste management being my contribution to controlling an ecosystem. However, understanding ecology through a top down lens is something new to me.

Silliman’s article challenged this conventional idea of looking at our ecosystems through a bottom up perspective. Surprisingly, the top down idea controls the salt marsh communities. Through his experiment, he manipulated the consumer densities in the salt marshes, thus showing that the high plant production in salt marshes was a result of a trophic cascade lens.

What I found fascinating from Silliman’s article was that he posed a hypothesis, contrary to popular belief. Not only did he dare to present the idea, he believes that his findings supersede what was once believed with regard to plant growth. If only Silliman’s experiment were publicized more, it can have a profound effect. I am sure that I am not a minority in asserting that my effect on controlling an ecosystem is minimal. Perhaps with more publicity of his findings, others will acknowledge and recognize their consumer influence on our ecosystems, and moreover, reevaluate their actions with regard to ecology.

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A Traditional Theory Reconsidered -Silliman 2002

Many people assume most ecosystems are examples of a bottom up regulated system: that the primary producers, physical and chemical factors are what maintain the entire ecosystem and ensure the life of the consumers by controlling the ecosystem structure. Silliman and Bertness’ paper explains how this rule is applied too frequently, especially in salt marshes. In their paper they created an experiment to prove the existence of a strong top down consumer consumer amongst Littoraria (a type of sea snail) and Spartina (cordgrass) in southeastern coasts of the US.

Through the research done in their scientific experiment they have also shown the impact of eliminating a predator from its ecosystem may “indirectly alter the structure and function of intertidal marsh habitats.” This means their are also implications we have to be aware of when we kill predators for food or build on a natural ecosystem, kicking predators out of their habitats. Even though we think we may not be disrupting primary producers a lot of these ecosystems are actually top down regulated.

It’s interesting to see how they created a hypothesis that not only went against a common theory but actually completely contradicted one in many circumstances. This article opened up a new perspective to me and made me question other ecosystems which may come up more frequently in my other classes. Often we see things as a bottom up regulated system such as our food. But if we were to apply this to the human ecosystem do you think that it could be perceived as bottom up or as top down in terms of what organisms we depend on for survival? What about within the education ecosystem?

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Dinner at the Cost of Destroying the Environment

When we take resources from our environment, we don’t always consider the potential consequences.  Choices that seem like they wouldn’t affect the environment that much can actually cause far more damage than we realize.  Sometimes altering even one part of an ecosystem can throw the entire ecosystem off balance and alter it completely, generally for the worse.

Silliman’s and Bertness’s article discusses how altering one part of an ecosystem can throw off the entire ecosystem entirely.  Their article mentions how increasing or decreasing the number of a certain part of the ecosystem can alter the rest of the ecosystem.  Reducing the number of a species on the upper level of a food chain for example, can increase the number of species on the lower levels of the food chain.  Plant life can also be altered which can change the ecosystem type, altering the levels of certain chemicals in the environment, which in turn can affect the wildlife present.

Silliman and Bertness mentioned how overfishing off the east coast of wildlife such as crabs is severely affecting the stability of marshes.  The presence of blue crabs is crucial to the preservation of the marsh ecosystem.  Although crabs are considered a delicacy by many, we need to be more conscious of how much we take from our ecosystems.  If we take too much, there will be nothing left to take.

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It’s Not All About the Money

In Costanza’s article, it discusses the approximate economic value of ecosystem services. Apparently, the ecosystem services are worth trillions of dollars. Honestly, I don’t think there should be a price on a system that helps the growth of life. Certain ecosystem help certain animals survive. However, with human intervention like cutting down a forest, it would result in loss of habitat, food, etc. I feel like it is immoral to just destroy homes of innocent animals.

People shouldn’t change the quality or quantity of ecosystem services. We shouldn’t create new buildings, streets and bridges because we are ruining these ecosystems. Ecosystems are very important to the contribution to human welfare on this planet. There are so many benefits of conserving ecosystems compared to changing it into a man-made structure. In the article there is a long list of the benefits of ecosystem services , such as water supply and regulation, nutrient recycling, food production, raw materials and biological control. These benefits should outweigh the benefits for creating any structure.

This article reminded me of the controversy in Oyster Bay, which was mentioned by a classmate. A referendum was created to petition the sale of a property for the creation of a mall in Oyster Bay, which would be sold for $32 million. Right next to it is a Cerro Wire plot that is home to certain endangered birds and other species. Building a mall near this plot of land would cause harm to the animals and birds due to the increasing amount of pollution from cars and trash. I don’t think putting animals in harms way is worth the production of a mall. Sadly, the voters approved the construction of the mall and there will be consequences.

There already has been so much human intervention; so can we protect these ecosystems rather than destroy it.  Ecosystems are irreplaceable and therefore should be priceless.

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