Lecture 1: Global Environmental Change PDF

Lecture 1 Global Environmental Change Stuff about me (Prof. Janine Baijnath-Rodino)  goals of the course As a GE course in Physical Sciences, a key goal is to introduce students from all backgrounds to fundamental principles of scientific inquiry - how scientific research is...

Lecture 1 Global Environmental Change Stuff about me (Prof. Janine Baijnath-Rodino)  goals of the course As a GE course in Physical Sciences, a key goal is to introduce students from all backgrounds to fundamental principles of scientific inquiry - how scientific research is done, and how scientists work. We will use the science of climate change to do this – and it's important to your future! The main focus is on the science; policy will be a (minor) component (2-3 lectures). We will practice critical thinking skills and apply them to climate change issues. 3  Specific goals Provide the scientific background necessary to understand climate-related issues. Gain a scientific and quantitative understanding of the human influence on climate over the past 100 years and the coming century. Show the importance of science in shaping political debate on issues where accurate scientific information is critical.  Optional: general textbooks on climate change David Archer, Andrew E. Dessler, Global Warming: Introduction to Modern Understanding Climate Change the forecast No textbook is required, these are simply provided for those who wish additional background. Today’s Lecture – Global Environmental Change 1. Origins 2. Air Pollution 3. Land Use 4. The Oceans 5. Ozone 6. Climate Change 1. Origins  Who are we? Modern humans (Homo Sapiens) emerged in Africa, organized as hunter-gatherer societies (~200,000 years ago). The global environmental footprint of these societies was tiny because their numbers were so small. But a hallmark of their behavior was systematic exploitation of the local natural environment. Nearly all non-human species specialize in a particular food source; in humans, an unusually wide variety of plants and animals were consumed.  Out of Africa Arrival date, thousands of years before present Map of human migration out of Africa, from mitochondrial DNA patterns in present populations. Hunter-gatherer techniques allowed early humans to colonize an extraordinarily wide variety of environments, ranging from tropical savannah to polar tundra. By the end of the last ice age (15,000 years ago), humans inhabited all land masses. Data based on MITOMAP http://www.mitomap.org/WorldMigrations.pdf  Out of Africa Arrival date, thousands of years before present The fact that humans survived in so many habitats is a testament to the success of our species that is revealed well before civilization developed. It is also an early indicator of our unique ability to exploit natural resources creatively and intensively. NOTE: Mitochondrial DNA is passed from mother to child, and differences across populations are proportional to the time since the populations diverged. Data based on MITOMAP http://www.mitomap.org/WorldMigrations.pdf  Human population since “civilization” began Figure: R. Stewart "Oceanography in the 21st century" 8.1 billions as September 2023* Civilized life began shortly after humans reached all the continents. Human population has risen steadily since then and exploded within the last few hundred years. This is one of the factors behind extraordinary pressure on the planet’s resources. *United Nations data  The internal combustion engine Fossil fuels substituted human muscle or renewable energy such as water to power production. This was facilitated by the development of the combustion engine in the late 18th century. Every sector of the economy was revolutionized: transportation, construction, agriculture, and manufacturing. It enabled rapid population growth and prosperity. It also supercharged natural Watts steam pumping engine, invented ca. 1776 resource exploitation.  The Haber–Bosch process The Haber-Bosch process is chemical process that converts atmospheric nitrogen gas (N2) into ammonia (NH3). Ammonia is an excellent fertilizer (it provides N used to make amino-acids and build proteins). Today it is carried out at industrial scale (~4% of natural gas sources are used to fuel it). It made food production by agriculture much more efficient, supporting rapid population growth. Today about ½ of the N in the human body was produced by this industrial chemical process! First Haber-Bosch reactor at the Oppau plant in 1913 2. Air pollution  The United Kingdom – 19th century Burning of coal to power manufacturing created terrible “smog” in industrial cities, such as London.  Los Angeles – 20th century Image: switchboard.nrdc.org The Los Angeles region developed poor air quality in the 20th century due mainly to the reliance on gasoline-burning automobiles.  China and India – 21st century Beijing CHINA Image: NASA MODIS, Oct. 16, 2002 Though air pollution is a worldwide problem, the current epicenters are China and India, where reliance on coal-fired electricity plants to power manufacturing has created an air pollution problem on a continental scale. 3. Land use  Deforestation Deforestation in Ecuador by bulldozer. Photo by Stig Dalstrom The removal of forest, usually to use the land for a different purpose. About 80% of deforested land is used for agriculture.  Progression of tropical dry deforestation in Bolivia from 1975 to 2000 June 17, 1975 July 10, 1992 August 01, 2000 Dark areas show the native dry tropical forest. Light-colored areas show soybean fields cultivated for export, mostly funded by foreign loans. Images: U.S. Geological Survey Landsat 2 MSS Human impact on forest distribution as of the year 2000 https://ourworldindata.org/deforestation Image: World Wildlife Fund Green areas show original distribution, dark green is what remains of that. Light green areas have been converted to agriculture.  Facts about deforestation Deforestation occurs at a rate of roughly 150,000 square km per year worldwide (every 3 years, an area equivalent to the state of California disappears). Tropical forests once occupied 16 million square kilometers of the earth's surface, but now cover only 8 million. In many countries the rate of deforestation is accelerating. For example, most of the forested areas of Bangladesh, India, the Philippines, Sri Lanka and parts of Brazil's rain forest could be gone well before the end of the century. Only in the Congo Basin and some of the more isolated areas of the Amazon Basin does the forest remain largely intact. But for how long?  Monoculture agriculture and industrial farming Many areas that did not host forests have also been converted to agriculture, such as the U.S. Great Plains. Wherever industrial agriculture has become the norm, one species of plant grows over a huge area, supporting very few other plant and animal species.  Monoculture agriculture and industrial farming Other species, especially insects, are also systematically eliminated by agricultural practices. Effectively, monocultures tend to eliminate biodiversity (the number of different species living in a given environment). As we will see, industrial agriculture has an impact on climate as well. 4. The Oceans  Overfishing Modern fishing methods have led to some spectacular collapses of regional fisheries. An example is the collapse of the enormous cod fishery off the coast of Newfoundland.  Modern Fishing Photo: Jon Anderson, Smithsonian Trawlers such as the one pictured here are the norm for commercial fishing. Fish are caught with enormous nets, including many unwanted species; processing is industrialized, and occurs on the ship. Today, most fish stocks are relatively well-managed in industrialized nations (including the US). However, stocks in both developed and developing countries are depleted or collapsed; the “high-seas” are also unregulated.  Multiple stressors Great Barrier Reef, Australia Most marine ecosystems are under stress from human activities. These include pollution, agricultural runoff and fishing, but also ocean warming and ocean acidification. Coral reefs in particular are very sensitive to marine heatwaves – we have observed much more frequent bleaching events over the past decades!  Multiple stressors Great Barrier Reef, Australia Coral reefs are communities of tiny animals that secrete calcium carbonate (CaCO3) and collectively create vast hard structures. The structures support about 25% of the ocean’s species.  Multiple stressors Great Barrier Reef, Australia Warming temperatures have caused a series of massive heat-related stress events (bleaching). 2014-17: 75% of reefs globally were affected including loss of ~30% of the northern great barrier reef's shallow water corals. Ongoing ocean warming and acidification pose a threat for reef-building corals. e.g., https://coast.noaa.gov/states/fast-facts/coral-reefs.html  The big picture human impact on the ocean red = high impact blue = low impact It is much more difficult to observe and quantify human impacts on the ocean compared to land. This is a recent attempt to map out where the greatest impacts are occurring; most of the ocean is affected by humans! (Halpern et al. 2008.) 5. The Ozone Hole