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End of Ecosystems: Nutrient Flow Beginning of Environmental Crisis Lecture 12 Principles of Ecology College of Forestry, Guangxi University Eben Goodale Today and next Tuesday 1. Finish ecosystems by talking about nutrient flow. 2. Move to higher levels: “applied and large-scale ecology” 3. Introduce environmental challenges and global challenges. 4. Talk about conservation biology as one response. 5. Talk about landscape ecology and management as another response. Today leave 45 minutes for writing. Tuesday leave 1 hour for review for Midterm. Saturday May 16 final exam! Moving up a Layer: Definition of an Ecosystem Ecosystem Characteristics of the ecosystem That we’ll talk about: - Productivity - Energy flow - Nutrient flow What is a nutrient(养分)? C is definition of organic molecule. Remember N and P were limiting nutrients of NPP on land and in sea. What is a nutrient? C:N ratio measures nutrientrichness, as carbon usually structural, Whereas N is nigh energy. Animals << plants because more N. Nutrients are in the air • Some nutrients like carbon (CO2), oxygen (O2) can be fixed(固定) by living things from the air. • But other nutrients like nitrogen (N) can not be: N2 is very plentiful(丰富) but difficult to get N out of. P not in atmosphere. • Only certain kinds of bacteria(细菌) able to fix N, as we will see… Nutrients are in the ground • Mineral supplies. • Rocks are called “parent materials”… • Nutrients slowly come out of them due to weathering风化作用 (slow breaking down of rock). Nutrients are in the ground: soil • Decomposition is an important process that makes dead things like leaf litter soluble溶解 (available in water) to living organisms. • Strongly dependent on temperature. Nutrients are in the ground: soil • Soils different in particle size. • Different soils are better able to hold water and nutrients. • Leaching(淋溶) is the loss of nutrients from soils carried away by water. Medium: silt Smallest: clay Largest: sand Nutrients are in the ground: soil • Soils develop over successional time. • The more weathering, decomposition the better the soils. • Poor soils in tropics where decomposition so quick, all nutrients leach out. Nutrients are moved within the organism • Most nutrients in leaves. • Chlorophyll reabsorbed(重吸收) before leaf dropping. • 60-70% of N, 40-50% of P saved this way. Nutrient cycling(循环) How nutrients are moved between atmosphere, rocks, soils, water, living organisms. Rocks Soil Basics of nutrient cycling • Reservoir(容量) or pool: we can define as a part of the cycle (e.g. atmosphere, soil) in which a nutrient stays for some time. • Residence time(停留时间): the average time a substance spends within a reservoir. • Flux(流量): movement from one pool to another The water cycle Reservoir Average residence time Oceans 3,200 years Glaciers 20 to 100 years Seasonal snow cover 2 to 6 months Soil moisture 1 to 2 months Groundwater: shallow 100 to 200 years Groundwater: deep 10,000 years Lakes (see lake retention time) 50 to 100 years Rivers 2 to 6 months Atmosphere 9 days Cycle is fairly quick (except for ground water, deep ocean circulation) Phosphorus (磷)(P) • Needed for DNA, ATP • Little in atmosphere (just dust, mostly from human activities) so most derived from weathering of rocks. • Most important/limiting in aquatic ecosystems, tropical terrestrial habitats Phosphorus Cycle: the numbers are 1012 g P or fluxes as 1012 g P per year Amount in pool in box. Fluxes are the small numbers next to arrows Very little in atmosphere. Huge pool in marine sediments. Marine sediments mined by humans. 4 times the amt of natural weathering. Nitrogen Note: a different kind of bacteria, sends N back to atmosphere… • Nitrogen: used for DNA, proteins • Nitrogen fixation done by some free-living bacteria and others associated with plants, especially legumes(豆科植 物). In some agriculture, legumes Added because of N fixing properties. Nitrogen Cycle: the numbers are fluxes as 1012 g N per year Orange shows human contribution Natural N-fixation ~ What’s lost by denitrification Human fix N2 by HaberBosch process (industrial way to make fertilizer) 工业固氮 Carbon cycle • Central “nutrient”: – closely bound to energy – bound to N – makes up structure of most organisms: 50% of dry biomass • Major carbon storage, or sinks: – slow-decomposing compounds in soil – bicarbonate in the ocean – fossil fuels – wood Carbon Cycle: the numbers are storage as 1015 g C or fluxes as 1015 g C per year Gaseous气态的 phase: wellmixed. Atmospheric concentration 350 ppm (preindustrial 250 ppm) Aqueous液态 的 phase: dissolves in ocean water (bicarbonate HCO3). Solid phase固态的: residence times of carbon in soil, and in plants, from weeks to centuries Human influence on nutrient cycle and its outcome • As we move to talking about conservation biology and global ecology, we will talk more about how humans have altered nutrient cycling, especially: • N deposition(沉淀物) (added to atmosphere by industrial activity, then falls down). • CO2 increase and global warming. Manipulation and disturbance of ecosystems One local scale human influence on ecosystems is that human activity Like logging can influence what much leaching occurs, and thus How much of the nutrients of an ecosystem are lost (flow out with water). Famous studies have calculated nutrient cycles for a whole catchment area. Ecosystem Modeling Looking at ecosystems like a machine and see how human disturbance Influences them. Today and next Tuesday 1. Finish ecosystems by talking about nutrient flow. 2. Move to higher levels: “applied and large-scale ecology” 3. Introduce environmental challenges and global challenges. 4. Talk about conservation biology as one response. 5. Talk about landscape ecology and management as another response. Today leave 45 minutes for writing. Tuesday leave 1 hour for review for Midterm. Saturday May 16 final exam! Moving up to the top! Landscape Describes how Different ecosystems Are put together in space We are also going to talk about environmental problems the earth faces at a global level. th 6 Are we in the major extinction event? Rates of extinction are 100 to 1000 times what the normal rate is according to the fossil record. From Barnosky et al. 2011 Humans have been causing both extinctions (灭绝) and introductions(迁移) of animals Introduced plants (to US) # of species of birds on Pacific island (many were flightless) Introduced plants could be intentional(有意的) or not. In what ways are they non-intentional? They can cause much destruction The environmental crisis: man’s impact on the globe CO2 Climate Change Some changes we will discuss • • • • • • • • Habitat loss Species invasions Overharvesting Global climate change Nitrogen deposition Toxin accumulation Ozone hole Acid Rain A happy ending? Habitat Loss(生境丧失) 2006 Worst right now in tropics (bad in boreal forests too but less diversity) 2002 Habitat Loss 3 factors are here associated: Habitat loss: less natural land cover. Habitat fragmentation(破碎) : smaller, more isolated pieces. Habitat degradation(退化): what remains has been changed to be poorer quality. We will talk about fragmentation next lecture when we talk about landscapes. Habitat loss: what does this mean for biodiversity? Large animals with the greatest Space requirements most affected. The hammerhead, great white and thresher sharks have each declined more than 75% in last 15 years. (Baum et al, Nature, 2003) Last (2015) male white rhinoceros being guarded At the same time, we must remember that of the world’s 5-10 million species are plants and insects that are being lost before they are even discovered. Many species may already be “ghosts(鬼魂)” reduced to such low numbers that they will eventually go extinct. Habitat loss: population driver Habitat loss will be directly affected by population growth … Population predicted to peak around 10 billion in 2100 Habitat loss: life-style(生活方式) drivers Many developing countries like India increasing their consumption (消费) India has traditionally been vegetarian. but chicken consumption doubled 2000 to 2014. The Tata Nano, A $2000 car aimed at India’s middle class Next issue: Species invasions (入侵) • As we move around the globe,we move organisms, too, intentionally, and nonintentionally. • Species without their natural predators and pathogens can reproduce in remarkable ways Brown rat snake Zebra mussels (a) Brown tree snake, introduced to Guam in cargo (b) Introduced kudzu thriving in South Carolina Some well known invaders… economic damage can go into billions of dollars Next issue: overharvesting(过度捕捞) Includes: -Hunting of animals -Animal trading for pets -Extraction of medicinal plants Leads to: -“Empty forest syndrome” -Human “Allee effect”: the rarer an animal gets, more expensive it is ($45,000 for tiger pelt). Responses include: - Management of sustainable extraction (hunting permits). -CITES (Convention on International Trade in Endangered Species) Next issue: overharvesting(过度捕捞) • Overfishing, as we learned last class, is a major problem. Large predatory fish all declined Cod fisheries have collapsed http://www.montereybayaquarium.org/cr/seafoodwatch.aspx Forensic science and overharvesting • Using DNA technology to track down where animal products are coming from. Next issue: global warming(全球 变暖) If left unchecked, at current rate 1200 ppm By 2100 (source: NASA). CO2rates increasing and CO2 closely associated with temperature … Although not only greenhouse gas (methane, etc.) Tracking man-made CO2 • Carbon in 3 forms: C12, C13 (1%) and C14 (1 X 10-12 %) • Plants and fossil fuels high in C13, higher than other sources of C (e.g., deep oceans) C12/C13 ratio changing rapidly Global warming: effects Associated problems…. Sea level rising ~ 1.7 mm year Extent of sea ice in Artic … -10% Per decade From NOAA (www.ncdc.noaa.gov) Ocean acidification: may be big problem for things that have calcium carbonate structure like corals Global warming: predictions Predictions: Range of estimates from 1.8 to 6.0ºC increase by 2100, depending on control of emissions levels, among other factors. From NOAA (www.ncdc.noaa.gov) So many man-made source of C that solution to global warming will be complex! Effects of global warming not uniform Increase in temperature expected to hurt agriculture in developing, tropical regions. Next issue: Nitrogen deposition N fixation by humans now greater than natural fixation Nitrogen deposition Nitrogen deposition 1. N is a fertilizer so it increases plant biomass. 2. But unfortunately, it also decreases species diversity, because only a few species are well adapted to high N level. A famous experiment In England that has shown species diversity to decrease over 150 years. Other toxins Humans are producing thousands of chemicals, many of which have effects we do not fully understand. These toxins are concentrated as the higher the organism is in the food web. We’ve already talked about POPs (peristent organic pesticides) Some species are endocrine disruptors (内分泌干扰物): lower the natural fertility of wildlife. Eggs cells develop in frog testes after exposure to the common pesticide atrazine From Hayes et al. 2003 Some hopeful signs … The ozone hole: a problem addressed? The ozone layer (臭氧层) is very important for blocking UV radiation(紫外线) The largest ozone hole was recorded over Antartica in 2006 In the 1980’s, Scientists began to notice bigger and bigger holes in the ozone layer. It was shown that some of the loss of ozone was due to CFCs, chemicals used in refrigeration. Some hopeful signs … The ozone hole: a problem addressed? In 1987, the Montreal Protocol was signed, which gradually phased out CFCs. Recently, the hole in the ozone layer has slowly begun to decrease. Some hopeful signs: acid rain Part of the “Deposition” Problem, along with N Depoisition. Acid rain in the US has slowly improved With new policies on power plant emissions. Today and next Tuesday 1. Finish ecosystems by talking about nutrient flow. 2. Move to higher levels: “applied and large-scale ecology” 3. Introduce environmental challenges and global challenges. 4. Talk about conservation biology as one response. 5. Talk about landscape ecology and management as another response. Today leave 45 minutes for writing. Tuesday leave 1 hour for review for Midterm. Saturday May 16 final exam! Strategies of conservation • Endangered species conservation – Species by species approach • Multi-species habitat planning – Attempts to conserve large tracts with viable populations of most species – “No surprises” Myers et al. 2000 related to the second strategy (habitat planning). Primary reading • Myers et al. 2000 “Biodiversity hotspots of conservation priorities” Questions: - How do the authors define a hotspot? - Are there any in China and where? - How do the authors want their hotspot list to be used? Conservation Biology • The scientific study of phenomena that affect the maintenance, loss and restoration of biodiversity (genes, individuals, species, communities). • Conservation to be successful needs to combine biology with social sciences like politics, economics and physchology. Why conserve? Economic reasons Genes: Genetic variation is key to a species’ longterm viability and flexibility to change. Species: - Derived products - Biophilia and ecotourism - Product extraction from an environment that conserves species. Ecosystems: There are also spiritual and cultural - Ecosystem services. reasons to conserve Benefits of Diversity: Pharmacology Gila monster produces enzyme that binds to insulin, used in new diabetes drug Fungal endocyte that lives within Pacific Yew: source of Taxol. Polymerase from bacteria in hot springs used for PCR and revolutionized biotech Biophilia = our natural interest in biology. Can it pay the bills? Eco-tourism Tourism principle foreign exchange earner for 83% of developing countries; tourism up 20% from 2002-2007 (Global Ecotourism Conference, 2007) Problems: - But in most countries, tourism controlled by major (often international) businesses. -Have ecotourism promoters over-promised? Balancing extraction with biodiversity Micro-industries which can be performed on buffer of conserved forest. Rattan gathering in Myanmar Palm sugar tapping in Sri Lanka Honey collecting in Bangladesh Balancing extraction with biodiversity Plantation crops that conserve *some* of the biological diversity of an area. Shade coffee Cardomum plantation Ecosystem Services • Ecosystem services include – – – – – Purification of air and water Detoxification and decomposition of wastes Cycling of nutrients Moderation of weather extremes And many others • We get these services for free. Should we charge for their removal? • How do we place a value on such services? Ecosystem Services But is this realistic? Who pays? Ecosystem Services The NY watershed example: Bought land worth $1 billion; saved ~ $6 billion in new treatment plant. Ecosystem Services Debt for Nature swaps and the establishment of Costa Rica’s park system But politically and economically: are these even trades, and are governments “selling out” their people? Key concepts • Nutrients cycle between pools in ecosystems. Know the cycles of C, N and P. • Biodiversity is being lost at levels approaching a mass extinction. • Habitat loss is the largest problem, but other problems include invasive species, overharvesting and climate change. • Conservation biology’s mission is to minimize biodiversity losses.