Transcript Chapter 6
Chapter 6 Humans in the Biosphere 6 – 1 A Changing Landscape • What type of human activities can affect the biosphere? Earth as an Island • All of the organisms, including humans that live on Earth share a limited resource base and depend on it for their long term survival • To protect these resources we need to understand how humans interact with the biosphere Human Activities • Since we depend on the ecosystem for resources we must be aware that human activities can change the local and global environments • Among human activities that affect the biosphere include Hunting and Gathering Agriculture Urban Development The Tragedy of The Commons What was the tragedy? • It was the notion that any resource that is open to everyone – such as the air or parts of the oceans – will eventually be destroyed because everyone can use the resource, but no one is responsible for preserving it. 6 – 2 Renewable and Nonrenewable Resources • How are environmental resources classified? • What effect does human activities have on natural resources? Renewable resource • Can regenerate if they are alive or be replenished if they are nonliving • A renewable resource is not necessarily unlimited Ex.) water Nonrenewable resource • Cannot be replenished by natural processes Sustainable development • A way of using natural resources without depleting them and without causing long-term environmental harm • Human activities can affect the quality and supply of renewable resources such as land, forests, fisheries, air, and fresh water Land Resources • If managed properly, soil is a renewable resource • Soil, however can be permanently damaged if it is mismanaged Soil erosion • The wearing away of surface soil by water or wind Desertification • When once productive areas are turned into deserts • Caused by: • Farming • Overgrazing • Drought Sustainable Solutions to guard against these practices • Contour plowing • Leaving stems and roots of the previous years crop in place • Planting an unused field with rye Forest Resources • Forests are important because they • Provide wood • Are considered the lungs of the earth • Store nutrients • Provide habitats • Provide food • Moderate climate • Limit soil erosion • Protect freshwater supplies Deforestation • Loss of forests • Can lead to severe erosion Sustainable Solutions for Forest Management • Harvest mature trees selectively • Tree farms • Tree geneticists Fishery Resources • Fishes and other animals that live in water are a valuable source of food for humanity Overfishing • Harvesting fish faster than they can be replaced by reproduction Sustainable Solutions for Fisheries • The US National Marine Fisheries Service uses data on fish populations to create guidelines for commercial fishing • Aquaculture – raising aquatic animals for human consumption Air Resources • Air is a common resource that we use every time we breathe • The condition of air affects peoples health • The preservation of air quality remains a challenge to modern society Smog • A mixture of chemicals that occurs as a gray-brown haze in the atmosphere Pollutant • A harmful material that can enter the biosphere • Many combustion processes, such as the burning of fossil fuels, releases nitrogen and sulfur compounds • When these compounds combine with water in the atmosphere they produce nitric and sulfuric acids which fall to the earth as acid rain Freshwater Resources • Americans use billions of liters of freshwater everyday • Although water is a renewable resource, the total supply of freshwater is limited • For this reason, protection of water supplies from pollution is a major priority Sustainable Solutions • Protect natural systems involved with the water cycle Ex.) wetlands and forests • Water treatment facilities • Drip irrigation Protect natural systems involved with the water cycle Ex.) Wetlands and Forests Water Treatment facilities Drip irrigation 6 – 3 Biodiversity • What is the value of biodiversity? • What are the current threats to biodiversity? • What is the goal of conservation biology? 6 – 3 Biodiversity • Variety is the spice of life • But variety in the biosphere gives us more than just interesting things to look at • Human society takes place in local and global food webs and nutrient cycles • For that reason, out well being is closely tied to the well being of a great variety of other organisms Biodiversity • (Biological diversity) – the sum total of the genetically based variety of all organisms in the biosphere Types of Biodiversity • Ecosystem diversity – the variety of habitats • Species diversity – the variety of species • Genetic diversity – the variety of genetic info carried by all the organisms The Value of Biodiversity • Biodiversity is one of Earth’s greatest natural resources • Species of many kinds have provided us with… • Food • Industrial products • medicines Threats to Biodiversity • Human activity can reduce biodiversity by: Altering habitats Hunting species to extinction Introducing toxic chemicals Introducing foreign species Endangered Species • A species whose population is declining and is in danger of becoming extinct Extinct • When a species disappears from the biosphere Habitat Alteration • When land is developed, natural habitats are destroyed Habitat fragmentation • When development split ecosystems into pieces Demand for Wildlife Products • Throughout history, humans have pushed some animal species to extinction by hunting them for food or other products • Today, endangered species are protected by laws • Unfortunately it is difficult to enforce laws in remote wilderness areas Pollution • Many forms of pollution can threaten biodiversity • One of the most serious problems occurs when toxic compounds accumulate in the tissues of organisms Ex.) DDT Biological magnification • When concentrations of harmful substances increase in organisms at higher trophic levels in a food chain Introduced species • One of the most important threats to biodiversity today is introduced species Invasive species • Plants and animals that live in environments they are not native to Q: Why do invasive species reproduce rapidly and quickly take over their new habitat? A: Their new habitat lacks the predators and parasites that control their populations “back home” Conservation • The wise management of natural resources including the preservation of habitats and wild life Strategies for Conservation 1. Managing of a single species Ex.) captive breeding Strategies for Conservation 2. Protecting entire ecosystems Ex.) setting land aside Conservation Challenges • Protecting resources for the future can require people to change the way they earn their living • The challenge is to maximize benefits while minimizing economic cost • But an ecological perspective tells us that if we don’t take some difficult steps today, some resources may disappear and jobs that depend of that resource will be lost permanently 6 – 4 Charting a Course for the Future • What are two types of global change of concern to biologists 6 – 4 Charting a Course for the Future • For most of human history, environmental change was a local affair • Today, most of Earth’s land surface has been altered by human activity • In order to plan a sound environmental strategy for the 21st century, we need data provided by research Ozone Depletion Ozone layer • Part of the atmosphere that contains a relatively high concentration of ozone gas (O3) • The ozone layer absorbs a good deal of harmful ultraviolet or UV radiation from sunlight before it reaches the Earth’s surface • Over exposure to UV rays causes: • Sunburn • Cancer • Damage to eyes • Decreased resistance to disease Early evidence • Satellite images in the 1970’s first showed the hole in the ozone layer over Antarctica • Evidence also showed that chlorofluorocarbons or CFC’s could change the ozone layer One Solution • Reduce the use of CFC’s • Many CFC’s are now banned Ex.) Montreal Protocol signed 1987 Global Climate Change • All life on Earth depends on climate conditions such as temperature and rainfall • That’s why many ecologists are concerned about strong evidence that Earth’s climate is changing • Since the late nineteenth century, average atmospheric temperatures on Earth’s surface have risen about 0.6 degrees Celcius • Since 1980 average temperatures have risen .2 and .3 degrees Celcius • The 1990’s were the warmest decade on record • 1998 was the warmest year since record keeping began Global Warming • Increase in the average temperature of the biosphere Evidence of Global Warming • If is believed that the current warming is related to human activities that are adding CO2 and other greenhouse gases to the atmosphere • The burning of fossil fuels combined with cutting and burning of forests worldwide is adding carbon dioxide to the atmosphere faster than the carbon cycle removes it • As a result, the atmosphere’s natural greenhouse effect is intensified causing the atmosphere to retain more heat Possible Effects of Global Warming • Computer models based on the trends seen in the data suggest that average global surface temperatures will increase by 1 to 2 degrees Celsius by the year 2050 Q: What might this mean? A: • Sea levels may rise enough to flood some costal areas • More droughts in North America • New organisms will be able to live in places where they once could not • Other organisms may become threatened or extinct in areas they once thrived The Value of a Healthy Biosphere • Human society depends on healthy, diverse and productive ecosystems because of the environmental and economic benefits they provide • People can help maintain the health of the biosphere without drastically changing their lifestyles if they make wise choices in the use and conservation of resources The Future of the Biosphere • Studies of human impact on the environment are not about predicting disaster • You have seen how research has lead to action which is fixing the mistakes of the past • Remember, the biosphere is strong and we humans are clever. Both humans and natural ecosystems can adapt to change of different kinds