Weekly summary of Tropic101x as posted by student Lucia_Agudelo. With minor grammatical and content edits by Tropic101x team

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1 Weekly summary of Tropic101x as posted by student Lucia_Agudelo With minor grammatical and content edits by Tropic101x team Summary of Week 4 MARINE ECOSYSTEM SERVICES LECTURE These are the services that natural ecosystems provide to humans for free: Mangroves can provide wood. Coral reefs provide a provisioning service of food (reef fish and other species). Pharmaceutical products. Mangroves and the mud that sits underneath them attenuate the amount of wave and storm surge energy that hits the coast. Tourism. Cultural benefits. The Millennium Ecosystem Assessment went through a fairly extensive categorization of ecosystem services: Cancun Mexico: Mangrove removal for hotel development has been drastic. The process of all that dredging can have damaging impacts all of its own. It leads to a lot of sediment entering the water that can smother coral reefs and essentially cause coral mortality. If you kill the coral, this then reduces the natural ability of the ecosystem to act as coastal defense and increases the amount of erosion that happens on the coastal zone. Why value ecosystem services? Accounting national natural resources Monitoring and corrective action Engaging community Generating financial support for conservation

2 The state of an ecosystem might be the amount of living coral or the complexity of the reef. That state supports a function and it's that ecosystem function that we're often interested in. The function provides a service to people. These things can be reinforcing so if we do have a system of a healthy reef with prolific function that allows us to generate a good livelihood. Biologists and ecologists often work to forge this link between the state of a system and its function. Then social scientists and economists can link the function of a system to the services and benefits that the ecosystem provides to people. Only one species of fish has a very strong, almost obligate, dependency on there being mangrove and that is Scarus guacamaia, the rainbow parrotfish. Juveniles are almost always associated with mangroves and you find the most adults where mangroves are in reasonably close proximity. Blue-striped grunt and the French grunt, number of adult fish on the reef can be many times greater where you have mangroves in the system. So what this is telling us is that, the provision of a healthy mangrove environment can lead to a very significant increase in the number of adult fish that people can harvest. So the mangrove is providing a function which is a nursery habitat to the coral reef fish, and then that function is helping to sustain the service of a reef fishery. LECTURE Economists have a number of different ways of valuing ecosystem services (market services): Travel cost Hedonic pricing Replacement cost Avoided cost of damages Contribution of fish to a local economy

3 Methods to value non-market services: Contingent valuation Choice modelling When you take all these economic values and put them together for coral reefs globally, the total value of coral reef ecosystem services around 30 billion US dollars per year. Some challenges in valuing ecosystem services: Drivers of change Understanding changes in ecosystem state Multiple services from an ecosystem

4 We might want to know the relationship between fisheries productivity and the complexity and health of a coral reef, now at this point we have no idea what the shape of that relationship is. Is it a linear decline? Is it curvilinear? Mangrove services: Nursery and adult fishery habitat Fuel wood and timber Protection from erosion and disaster Carbon sequestration Traps sediment This study was done in Thailand looking at the value the value of mangroves: LECTURE Belize in Central America is at little jewel of the Caribbean. One of the techniques people are using in Belize to try to value ecosystem services in a spatially explicit way is to use a tool known as InVEST The first thing that you would do in developing a model of the service of recreation is gather some spatial information:

5 Then you take all of this information and you can combine it into a simple model that allows you to essentially predict where people are going to undertake their recreation. In order to estimate the number of visitors, you would look at how much those visitors are spending and then that essentially gives you a value for the recreation at a particular location. In order to incorporate this with an evaluation process, we need to think about an appropriate strategy. You need to think about the scenarios for future development. We have a variety of options and decision makers always need to have options to pick from. The question is: what are the consequences of each of those options? A conservation scenario: how might future activities in Belize develop, especially on the coast? They might choose a very conservation-orientated strategy where they

6 prioritize the good health of the ecosystem and allow less development. They might focus on development and allow development to run rife. Finally they might consider an intermediate solution which, in this case, was termed informed management where we try to seek a compromise and get a bit of everything. Imagine what these different scenarios would look like and create maps of how those would unfold. Then the challenges are to relate these to your models and predict what that would mean for future ecosystem services. A comparison between the current values and the informed management values. So the best development scenario of the three that were put on the table is the one that was a compromise between conservation and development.

7 LOCAL HUMAN IMPACTS LECTURE Ecosystems have always been disturbed: whether it's cyclones causing damage or earthquakes that can shake corals free and knock mangroves over. El Niño events naturally increase the temperature of water around coral reefs and this can cause coral bleaching. In 2010 there were 130 million square kilometers of land on earth. Only 5% it is near the coast but nearly 40% of people on earth live within that small coastal area. This means that the density of people living at the coast is much greater than that living farther away from the coast. A very widespread problem is the erosion of land into rivers: 1. When we remove mangroves sediment flows out onto seagrass beds and sometimes even as far as the coral reef. 1. When you replace mangroves with something like sugar cane, every time there's a rainfall event a lot of that sediment enters the river it runs offshore. You can imagine it floating around near the surface of the water. As it does that, it blocks sunlight.

8 A second consequence of having a high density of people developing the coast area is nutrient runoff, mostly nitrogen and phosphorus, that are finding their way from the land into the rivers out into the coastal zone. In developed countries we're still increasing the amount of fertilizer use. About half of the nutrients we apply for agricultural purposes find their way somewhere else into the environment. The combined effects of nutrient and sediment runoff is called Eutrophication. Extra nutrients entering the water are going to be taken up by phytoplankton. Having more phytoplankton in the environment reduces the amount of sunlight. If you have a surplus of plant growth, because there's more nutrient, and you don't have enough animals cruising to consume it, what happens is much of that plant growth dies rather than being eaten and then becomes detritus that's broken down by bacteria, and having lots of bacteria in an environment can increase the risk of disease. A greater concentration of detritus, sediment and nutrient can increase the stress on animals and plants and make them more susceptible to disease or reduce their reproduction. A big increase in the amount of dead plant matter will be covered with bacteria. That bacteria respires (breathes) and as it does so, it uses up oxygen in the environment. When that happens, the system becomes anoxic and we end up with hypoxia a low oxygen environment that can kill many organisms. LECTURE Clearing habitat: removing mangroves allows more and more soil to wash off into rivers and into deltas and makes them shallower and shallower.

9 A second mechanical damage is dredging. We want to create sediment and sand that we can then sort of dump into shallow coastal waters to create new land, reclaim land that we can then build on. One of the biggest sources damage occurs through fishing and the use trawls. The trawls are moving along the seabed. And as they move along they can very seriously damage the seabed and anything that's living there. This is a graph of global fisheries catch. From about 1950 to 1990 catches were increasing. Then from 1990 onwards they level off. So we're expending a much greater amount of effort to catch the same amount of fish. It means that the fishery is much less productive now than it used to be. If we go back to 1974, at that time only about 10% of the world's fisheries were considered overexploited. Now that number has risen 3-fold to 30%.

10 We like to catch and eat big fish. One of the problems that catching big fish causes is that big fish play a disproportionately large role in sustaining the next generation. Typically what we do in many fisheries now is to fish a slot on intermediate-range sized fish to try to minimize the impact on the sustainability of the fishery. Dynamite fishing: using dynamite is very dangerous to fish and it has a long-lasting negative effect on the ecosystem. LECTURE Alien species are those that usually we have introduced into an area that were never there historically. Alien species or the indigenous species can become a pest and those are called invasive species. Worldwide about 57% of invasive species are considered to be harmful. About 84% of the globe is currently affected by invasive species. For example, around Florida and the Bahamas, people started to see lionfish. Over a period of five or six years lionfish spread all through the region and up the eastern seaboard of the United States. They re an almost perfect invasive species because they reproduce very rapidly, are covered by venomous spines, so they have few natural predators in this environment, and are voracious predators that eat almost any kind of small fish or invertebrate.

11 About 60% of the world's reefs are really threatened. When we put these threats together it results in a shift in the balance of these coral reef ecosystems from coral dominance towards seaweed dominance or algal dominance. Positive local human impacts: Preservation of ecosystems Restoration of damaged systems There are some examples where people have taken great strides to improve their lot: Philippines in the island of Apo, 1980's: they took a decision to set up a small protected area where there would be no fishing. Over the next twenty years or so the biomass (the total weight of fish) inside that reserve has increased dramatically without really having a negative effect on people's livelihoods because there was still enough area for them to continue fishing. Honduras: smaller scale fishery where people are free-diving from the surface of the water in fairly shallow conditions, snorkelling to collect lobster. To provide habitat for those lobsters they will put casitas or small shelters on the seabed to help maintain the lobster population. GLOBAL HUMAN IMPACTS LECTURE Planetary temperature is a consequence of the ratio between incoming and outgoing radiation, and the absorption of energy by land, sea, and atmosphere. At equilibrium, incoming and outgoing radiation to the earth should be equal, and if so, the temperature will be stable. Change the magnitude of any one of these arrows and planetary temperature will change.

12 Incoming and outgoing radiation can change as a result of a number of variables: Distance from the sun/solar intensity can change. Changes in vegetation, clouds and ice fields can change the amount of energy that is reflected back into space. Gases such as carbon dioxide and methane absorb infrared radiation, resulting in a greater retention of energy within Earth s system. During warm phases, with Earth being slightly closer to the sun, warm interglacial periods have occurred. This variability is referred to as the Milankovitch Cycle, and it s main driver is solar radiation. Conversely, that we see in the current period of rapid anthropogenic (human-caused) climate change, where CO2 and other greenhouse gases are increasing and are driving a change in planetary temperature - not the reverse. 150 years ago the heat balance of the Earth began to change: Atmospheric concentration of greenhouse gases such as carbon dioxide and methane began to increase as a result of the escalation of the use of fossil fuels such as coal, oil, and gas as the Industrial Revolution took place. Average temperature of our planet began to increase in response to the increase in atmospheric concentrations of carbon dioxide and other greenhouse gases. Concentration of carbon dioxide has increased to 400 ppm. In response, average global temperature have increased by 0.8 C. Major changes associated with global warming: Land temperatures are increasing at the rate of around 0.2 C per decade. Rainfall has been increasing in some regions while decreasing in others. Storm systems have become stronger in some areas. Impacts on human infrastructure form storms and floods have increased significantly. Characteristics of the ocean have changed in the following ways over the past century: Sea levels have risen by around 30 cm. Ocean temperatures have increased on average by 0.7 C. Summer sea ice in the Arctic has decreased 50-75%. Oxygen levels are decreasing in the bulk ocean.

13 Oceans have become much more stratified in many regions, reducing the mixing and nutrient regeneration. Adding CO2 to the atmosphere is decreasing the ph and the concentration of carbonate ions - leading to a decrease in calcification and negative effects on the calcium carbonate balance of coral reefs. The Intergovernmental Panel on Climate Change (IPCC) was established in 1998 to assess the scientific, technical, and socioeconomic information relevant to the understanding of the risk of human-induced climate change. LECTURE Climate change in tropical oceans: Average temperature of tropical oceans has increased by 0.7 C. Tropical oceans have become acidified by 0.1 ph units. Decrease in the concentration of carbonate ions of around 26%. Oceans have been expanding and sea levels have risen by about 30 cm on average. More moisture in the atmosphere is leading to more intense rainfall events. Water column is becoming more stratified which is a consequence of warm water being less dense than cold water. As high latitudes are warming, the frequency of days during which frost occurs is decreasing - potentially removing one barrier to the expansion of mangroves to higher latitudes. Climate change is therefore also likely to affect nutrient availability, salinity, humidity and rainfall - all of which will have impacts on mangrove growth, resilience to

14 sea level rise, and processes that maintain carbon dioxide storage within the rich muds associated with mangrove ecosystems. Mangroves are likely to be victims of so-called 'coastal squeeze', being caught between a rising sea and human infrastructure barriers. Mid-range projections of changes to the climate in tropical coastal areas suggest a potential loss of 10-20% of mangroves over the next years. Seagrasses are also important components of tropical coastal ecosystems and provide ecosystem goods and services that have recently been estimated at $1.9 trillion per year in the form of nutrient recycling; primary productivity; habitat for thousands of fish, bird, and other species; and a major food source for endangered manatees, dugongs, and green turtles. Like other tropical coastal ecosystems, seagrasses are being heavily impacted by human activities such as coastal development and intensified coastal agriculture. LECTURE Impacts of ocean warming and ocean acidification on coral reefs: Coral reefs across the tropics and subtropics have been rapidly retracting at a rate of around 1-2% per year. Local factors such as overfishing and coastal pollution are important, rapid ocean warming and acidification are fast becoming the major drivers of change. Mass coral bleaching and mortality: Small changes in temperature were all it took to destabilize the all-important symbiosis between corals and dinoflagellates. Many stressors can cause corals to bleach, such as toxins, too much light, sudden salinity shocks and the role of temperature. When temperatures reach around 0.9 C above long-term summer maximum for a particular region, bleaching begins to occur. If temperatures were even warmer for longer, more intense coral bleaching and mortality would occur.

15 One of the most dramatic periods of mass coral bleaching and mortality, globally, occurred over nine months in This was associated with one of the strongest El Niño conditions ever recorded, with a massive reduction in upwelling and increase in temperatures across the central Pacific, including the Galapagos Islands and remote reefs of French Polynesia, such as the Tuamotu Archipelago, which has few other local human influences. Global Coral Reef Monitoring Network or GCRMN reported on average that 16% of the world's coral reefs had died over the nine months in In 2005, the eastern Caribbean experienced record sea temperatures and consequently experience mass coral bleaching and mortalityresulting in the loss of 30-40% of corals in the eastern Caribbean. In 2010, coral reefs across large parts of Southeast Asia also bleached. If the current rate of climate change is not reduced, then events like 1998 will become commonplace, indeed, considerably worse than If this happens, then coraldominated reef systems will be impacted on a regular basis by mortality events and won't have enough time to recover between those events. At this point coral reefs are likely to disappear within the next 30 to 50 years. Reefs are also unlikely to migrate to higher latitudes because temperature is not the only variable that determines the distribution of coral reefs. Light and the concentration of carbonate ions decrease as we get to higher latitudes, probably below the amount required for actively growing carbonate reef ecosystems. LECTURE Coral Reefs face challenges from ocean acidification: As carbon dioxide has moved into the upper layers of the ocean, the ph has decreased along with the concentration of carbonate ions. Reduced carbonate ion concentrations make the process of precipitating calcium carbonate into the skeletons of corals and other organisms much more difficult. Aragonite saturation state": is calculated by multiplying the concentration of calcium ions by the concentration of carbonate ions, and by dividing this product by the solubility constant for aragonite at a particular temperature. The highest aragonite saturation states exist at the lower latitudes and the equatorial regions of the planet. Look at these figures, the pink dots represent the location of carbonate reef systems today. The numbers in the corner of each slide represent the concentration of carbon dioxide in the atmosphere, being 280 ppm for the preindustrial period, 380 ppm today and 500 ppm in the future. Three important issues arise out of this analysis: Conditions within today's tropical oceans are highly unusual relative to the temperature and carbonate ion concentrations seen over the past 420,000 years. Rates of change in temperature and the carbonate ion concentration are the highest over this period of time.

16 Tropical oceans are rapidly approaching two important thresholds. The first being the concentration of carbonate ions at which carbonate reef systems will no longer be able to be maintained by calcification of corals and red coralline algae. The second being the thermal threshold above which corals will experience annual mass coral bleaching and mortality. This figure summarizes the transition from today. If we keep pushing up the concentrations of atmospheric CO2, we will get to a point in the right panel, where most organisms are struggling with the extra heat and acidity of tropical waters. At this point, and this is speculation, cyanobacteria may be the only obvious winners as coral reef ecosystems shift towards states which do not provide the ecological goods and services that the coral dominated reefs of today do. In this figure, the red family of models represents scenarios in which little is done to reduce emissions of carbon dioxide and other greenhouse gases. As you see, the average temperature change is around 5 C above the preindustrial period. The blue lines represent models which have a 60% chance of falling at or below a 2 C increase in average global temperature above the preindustrial period. If we are to achieve the blue family of curves, then we must rapidly reduce emissions of carbon dioxide and other greenhouse gases by 80% by Is there anything else we can do? We must deal with the problem of deforestation when it comes to mangroves if we are to give them the best chance of surviving rapid sea level rise. Reduce the amount of sediment coming into coastal regions. Reduce the extent to which we are damaging coral reefs through unsustainable coastal development, overfishing and pollution.