APES

Take home midterm 12/3/07

Question one: 746 words

a. Nitrogen fixation is the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) or Nitrite (NO₃^-) which makes nitrogen available to terrestrial plants and algae. Nitrogen is essential for all organisms because it is a major component in DNA and proteins. This figure demonstrates that the total amount of nitrogen fixed by humans (anthropogenic N fixation) has greatly increased to the point where it is greater than the highest estimate for natural nitrogen fixation. This graph illustrates the alarming increase in anthropogenic N fixation from 1960 to 1990. As illustrated by the graph, the primary causes of anthropogenic N fixation are: the use of fertilizer, the burning of fossil fuels, and the production of legume crops.

b. Natural nitrogen fixation is primarily done by bacteria. These bacteria live in soil, the stomachs of cud-chewing animals, or have symbiotic relationships with plants. One example of such a symbiotic relationship is found in the legumes (the pea family); the legumes provide nodules in their roots (habitat and food) for the bacteria and the bacteria provide nitrogen that the plant can use. Another natural though far less prevalent form of nitrogen fixation is high energy nitrogen fixation by lighting. This makes up only a small part of the total natural nitrogen fixation. Lighting fixes only 3x 10¹² grams of Nitrogen annually which is almost trivial when compared to the 140 x 10¹² grams fixed biologically.

c. The range of nitrogen fixation indicated by this graph is approximately 90 x 10¹² to 140 x 10¹² grams of nitrogen fixed on land annually. The range is probably this great because of the difficulty of measuring nitrogen fixation. The amount of nitrogen fixed in a given area of land is not constant over terrestrial ecosystems. As we saw by measuring nitrogen levels in the aquatic ecosystems of the Eel River and the wetlands, the amount of nitrogen in the water varied from no detectible nitrogen in the Eel to approximately 2ppm in the wetlands. The wetlands probably have a higher level of nitrogen then the Eel because of the denitrification by anaerobic bacteria that occurs in the wetlands or their proximity to human sources of Nitrogen. This example illustrates two problems in quantifying the amount of nitrogen that is fixed naturally. First, experimental testing of the amount of nitrogen fixed in a specific habitat will not translate to the amount of nitrogen fixed on a global scale. Secondly, it might be hard to distinguish the nitrogen that is present because it has been fixed by humans or the nitrogen that has been fixed naturally. Furthermore nitrogen cycles very quickly and the amount present at anytime can be influenced by seasonal patterns, disturbances, succession, invasive nitrogen fixing species, etc.

d. The doubling of available nitrogen is alarming to scientists or a myriad of reasons. First, such a great increase of nitrogen can have a devastating effect on plants. Nitrogen decreases biodiversity where plants have adapted to live in soil conditions with poor nitrogen quality because when more nitrogen becomes available they are out competed. In addition, an excess of nitrogen limits the presence of other nutrients because nitrogen can form nitric acid which leaches the calcium, magnesium, and potassium out of the soil. Only organisms which are adaptable to a high nitrogen level and an insufficient amount of these other chemicals may be able to survive. This creates an ecosystem in which a few species of plants and animals thrive and become dominate (limiting the biodiversity of the ecosystem). Unfortunately, these competitors are often non-native invasive species. The second primary concern that environmental scientist might have is the affect that an increase of nitrogen will have on air quality. Although nitrogen makes up 80% of earth’s atmosphere it is in the form N₂, when nitrite is converted back in to a gaseous though dentrification it is released as gaseous nitrogen (N₂) and nitrous oxide (N₂O). Nitrous oxide is a greenhouse gas that is one hundred and eighty times more reflective than carbon dioxide and thus probably contributes to global warming. The access of nitrogen can be a pollutant to human air supplies. The human alteration of this major biogeochemical cycle will not only affect terrestrial ecosystems, but also aquatic ones. The runoff of fertilizer into streams and the general increase in available nitrogen will increase algal production which can cause fish eutriphication and algal blooms. The increase of nitrogen concerns scientists because it will affect biodiversity, air and water quality, and climate change.

Question two: 516 words

a. Adding nutrients to the ocean would fundamentally increase primary productivity of algae. Nutrients such as iron which do not have a gaseous form are often limiting nutrients because they do not cycle quickly. Thus an increase of iron would increase algal productivity.

b. The rational behind this proposal is that when algae photosynthesize they absorb carbon dioxide from the atmosphere. This is true: 6CO₂ + 12H₂O => C₆H₁₂O₆ + 6H₂O. Some argue that the increase in primary productivity would help curb the effects of global warming. However, this is a drastic oversimplification of the issue. First of all, the effect of an increase of primary productivity will be short-lived because the algae will be limited by other resources (such as other nutrients, light, or space) and once the algae die and decompose, the carbon will mealy be released back into the atmosphere. Although the purported rational of this project is to stop global warming, this solution will mealy forestall the impact of global warming for a short time while creating a host of other problems that will ruin the aquatic ecosystem and have devastating global effects.

c. The addition of Iron, phosphorous, and other nutrients will have a disastrous effect on aquatic ecosystems. As is already a problem in costal upwellings where large amount of nutrients increase algal production, algal blooms can have a devastating effect on humans and marine life. Shellfish and the Ciguatera Fish consume the natural toxins present in the algae and pass the toxins along to their natural predators and the humans that consume them As has already been shown, the increase of algae production leads to fish eurtfication because the processes by which the algae are decomposed requires a lot of the dissolved oxygen present in the water which leaves very little for the fish who suffocate. The decrease in fish will reverberate up the food chain and affect the entire ecosystem. As with the addition of nitrogen to terrestrial ecosystems, the addition of iron will favor certain types of algae. This will lead to a loss of the biodiversity of algae and thus a loss of biodiversity of the many species of fish and other organisms that have coevolved with specific types of algae. The loss of biodiversity has many repercussions (pharmaceutical, evolutionary, etc.) and will greatly impact the ecosystem and its ability to respond to change. Finally, it must be taken into account that we can not foresee all the possible repercussions of this proposal. The increase of nutrients might have additional disastrous effects that we will only regret in hindsight. In conclusion, it would be far better to attempt to stop global warming by curbing out fossil fuel admissions, utilizing alternative renewable energy sources (like solar), and taking small steps to reduce our environmental impact (composting, recycling, reusing, changing light bulbs, etc.). The attempted alteration of biogeochemical cycles that have been in place for millions of years without proper research and testing is not only foolish, but could have cataclysmic consequences for the planet that could exacerbate the effects of global warming rather than mitigating the effects.

Question Three: 747 words

Dear Mr. President,

I applaud your decision to create a new National Park. National Parks are especially important in California because it is one of the 25 hotspots for biodiversity globally.

I’m sure you’ve heard of Smoky the bear. The underling message is that forest fires are not good for the environment. This is a common misconception; fires are often a key natural disturbance that actually increases biodiversity. They are regular enough that many organisms have adapted to them and require them for survival. Some conifers have serotinous cones that only open after a fire. Disturbances increase the biodiversity because they prevent a climax species from remaining the dominate species. When fires occur, the release the nutrients and minerals that were locked up in organic material and allow light to reach the soil. These conditions allow certain pioneer species (usually r-selected) to take place and the natural processes of secondary succession to begin. Disturbances often create patches of different stages of succession which increases the biodiversity at any given time. A medium level of disturbance such as that provided by fire will create the greatest biodiversity. In addition, if fires are prevented then the under story will build up and when a fire does enter the forest it will be decimating because it will be hotter and reach the crowns of the trees.

Some may think that national parks should be used for logging but this creates environmental problems that extend far past the local habitat destruction at the logging sites. Habitat loss is the number one cause of the decline of biodiversity. Logging companies create roads and destroy habitats. This creates a form a habitat loss called habitat fragmentation. There is a well documented relationship between the area of land mass and its biodiversity. Two small plots of land with a total area of land equal to a continuous larger area of land would have less biodiversity than the larger area. This is in part because of edge effects. A plot of land will experience edge effects because the conditions towards the edge of the ecosystem are more exposed and more vulnerable than the exterior and thus have less biodiversity. If a road is critical, I recommend that it is made in such a way that preserves the greatest continuous area of land.

Some may argue that national parks should be used for the grazing of livestock because grazing provides a natural disturbance. This is true, but only to a point. The grazing of the bison on the great planes did provide a critical natural disturbance that increased the biodiversity. However, the overall effects of cattle on the national park may decrees biodiversity. The fire creates the natural disturbance that the ecosystem needs as do the herbivores that are native to the habitat. The cattle increase erosion which can have detrimental effects on the water source (which is especially important if you are protecting the last non-damned watershed). Other than habitat loss discussed above, invasive species are the second greatest cause of the los of biodiversity. Therefore it is imperative that the amount of invasive non-native species in the park is limited. These non-native invasive species often alter the habitat in such a way as to make it inhabitable to native species. They spread quickly and are hard to remove (it is best if they are stopped as quickly as possible). However, I caution you not to use pesticides or biological controls against the invasive species. Pesticide runoff has disastrous consequences on the aquatic ecosystems and biological controls can often have horrible and unforeseen consequences (such as in the example of the cane toad).

The preservation of the water shed is critical for the biodiversity of the aquatic ecosystem and the riparian zone. It is important that there is no runoff of fertilizer, pesticides, or other urban waste into of the Smith River or the river itself. Such pollutants can cause algal blooms, fish eutriphication and will have detrimental effects on the ecosystem as a whole. Please note that this watershed should remain un-damned because scoring floods provide a natural disturbance that can be as beneficial as fires.

In addition to keeping these simple guidelines in mind while striving to maintain the biodiversity of the national park it might be helpful to consider the lager predators. If you can make sure the top predators have everything that they need in terms of habitat and range, you will be protecting everything that it depends on for survival.

Question Four: 744 words

a. Hawaii has acquired so many endemic species in part because it is an island. Species such as birds immigrates to the island long ago and then adapted to the unique ecological habitat of the islands. This is much like the adaptive radiation demonstrated by Darwin’s finches. In addition, some species can only survive on islands because of the lack of predation. For example, many birds that live on islands have lost their ability to fly because it is no longer necessary. Islands such as Hawaii are the physical manifestation of ecological islands. The geological history of Hawaii, its volcanic activity, and its great variety of climates all contribute to its biodiversity. There is so much biodiversity on Hawaii that it is considered one of the 25 global “hotspots” for biodiversity.

b. Invasive species have especially devastating effects on island communities because the native species have often never been exposed to anything like the invasive non-native species and are thus incredibly vulnerable. Snakes carried in the ballasts of airplanes could have a catastrophic effect on Hawaii’s birds much like the effects of the brown tree snake in Guam. On of the invasive species that is currently threatening Hawaii’s biodiversity is the Coqui frog. There are no native amphibians or reptiles and so the frog threatens many native and endemic insects and spiders which have not evolved to the predation of frogs. The consumption of these insects and spiders by the Coqui frogs puts them into competition with the native bird species and thus may lead to a decline of the native bird population. Another invasive species is the pathogen avian malaria. It was transported through poultry to Hawaii’s. Although the poultry have coevolved with the avian malaria and exhibit no symptoms, avian malaria has had a catastrophic effect on the native birds. As with the coqui frogs, the native species have no evolutionary adaptation to the introduced species. Because these native birds have no defense mechanism, the avian malaria has a 100% mortality rate. Invasive species are a major cause of the loss of global biodiversity, second only to habitat loss. The effects of invasive species are magnified on ecological islands and have had disastrous consequences for Hawaii’s endemic species.

c. The loss of Hawii’s 20,000 native species, half of which are endemic, could have disastrous and unforeseeable consequences for the human race. As Aldo Leopold said when speaking about the preservation of biodiversity, “the first principle of intelligent tinkering is to save all of the pieces”. Fundamentally, we do not know what benefits the endemic species of Hawaii will have because their future benefits are unknown; we must strive to preserve the biodiversity because of its potential future benefits. One of these potential future benefits is the use in pharmaceuticals. The drug that cures cancer may be found tomorrow in one of Hawii’s endemic species, but we may not recognize its value today. Another possible benefit is the use of new species in agriculture. Food sources found only on Hawaii may be used to bread with current crops to produce more viable or more resilient crops. Biodiversity is also important because in the event of change a greater biodiversity leads to a greater ability to adapt to change. In addition to the unforeseeable future benefits, biological diversity is important today in part because of its tourism value. Many travel to Hawaii to see the endemic species and study the native fauna. Ecotourism is an important economic incentive for the preservation of biodiversity. The effects of the loss of Hawaii’s species will have economic repercussions for those who benefit from the tourist industry and might have disastrous effects on the pharmaceuticals and agricultural products available to future generations. In addition, the decrease of biodiversity in Hawaii will make it harder for species to adapt to future environmental disasters such as climate change. Who knows, some of the species that can survive global warming may be endemic to Hawaii.

These are the wholly practical reasons that the preservation of biodiversity is important; however there are also many more subjective reasons why biodiversity can be important. Some believe that there is a moral justification for the preservation of biodiversity: that each species has a fundamental right to exist. Others appreciate biodiversity for its aesthetic pleasure. Many enjoy recreation in places with unique habitats. Ultimately, there are both practical and personal justifications for the preservation of biological diversity on Hawaii or on the earth as a whole.