农业生态学

Part I Context of Agroecology Chapter 1 Agriculture and Its Anthropocentric Sciences S. Wang and C. D. Caldwell “ but just simply distributing seeds and fertilizer， if that’s the plan， it’s going to fail long term.” —Howard Buffett Abstract The current model for industrialized agriculture is at a crossroads， characterized by degraded soil and environment， unbalanced human nutrition， food safety issues， loss of trust between consumer and producer， and finally sustainability at risk. By critically reviewing and integrating the definition and technological evolution of agriculture， agroecology links agricultural sciences with ecology to form an interdisciplinary and holistic science， generalized for steering an imperative agroecological transition in this anthropocentric era. Learning Objectives After studying this topic， students should be able to: 1. Explain the concept of the Anthropocene Era and why the earth may now be considered a “human planet”. 2. Describe three current important topics affected by how we do agriculture production. 3. Define the terms agriculture， agricultural sustainability， and agroecology. 4. Discuss how the discipline of agroecology has evolved and fits in the philosophy of agricultural sustainability. 5. Describe the three pillars of agricultural sustainability. 6. Explain why corn is a good symbol for the study of agroecology. 1.1 Introduction and the Anthropocene Era In May 1987， Jared Diamond published an article in Discover Magazine， entitled “The Worst Mistake in the History of the Human Race” in which he puts forward the thesis that agriculture， despite all its apparent positive effects on health， well-being， and survival of human populations， may have been a very negative turning point for humankind. He sees that agriculture has in many ways produced the disaster of social problems， disease and dysfunctional society. Nowadays， we would also add to that list of negatives associated with agriculture， problems of environmental degradation. Whether we agree with Dr. Diamond’s conclusions or not， human needs have certainly reshaped global ecosystems. Where previously there was a hunter–gatherer society， a drastic change occurred when farming was invented about 10，000 years ago. That is only about 300 generations ago and the world population was 1 million. About 5500 years ago， we developed cities and civilizations and the world population was about 5 million. Along came the Industrial Revolution about 150 years ago and the broader population had reached 1 billion. With World War II and the great acceleration 70 years ago， our population has blossomed. It took 50，000 years to reach the first 1 billion people; the last billion took 10 years. Technically， geologists would say that we are in the geologic Era called the Holocene. This is the period of the past 10，000 years of reasonably stable climate since the last Ice Age. We learn a lot from looking at layers of rock to determine the past geology of our planet. By examining the fossil record we can see the coming and going of species throughout the ages and speculate on what made some species survive and others not. It is interesting to speculate on what people in the future will tell about our time on this earth. From what we know at the moment， the geology will tell a story of extinct species， changes in the ocean chemistry， fewer forests and more deserts， dammed rivers and retreating glaciers， sunken islands， aluminum drink cans and plastic bottles， and perhaps large evidence of megaprojects like the oilsands in northern Canada. There are some geologists who， considering the present state of the world， would call this new era the Anthropocene; this is in recognition that humans have become geophysical forces with effects as much as asteroids and volcanoes have had in the past. If we consider that earth is now a “human planet”， we need to consider how agriculture has contributed to this new era. The invention or evolution of agriculture 10，000 years ago was perhaps triggered by climate change at the end of the Ice Age. Warmer， drier conditions were conducive to the growing of cereals (annual grasses) which were extremely successful due to their ease of production， their concentrated nutrition， ease of storage and transportation. This new culture depended on burning， shifting cultivation. However， with the domestication of chickens， pigs， and cows， there was an opportunity for the cycling of nutrients by putting manures back on the ground. This natural fertilizer worked well within such systems. However， as populations concentrated in groups， these natural fertilizers were not enough to avoid the starvation of masses. This led to the invention and widespread use of artificial fertilizers. The next steps in agriculture included extensive land clearing， increased use of water for irrigation (note that we now use 70% of our freshwater for agric