diffusion of Walmart. Contagious diffusion represents the outward spread from a point of origin, like rings emanating from a pebble falling in a pond. Explore the Walmart store openings dataset (1962−2006) in ArcGIS Online at https://arcg.is/0Cfy5a. Map by author. Data sources: Thomas J. Holmes. University of Minnesota, Federal Reserve Bank of Minneapolis, and NBER.
Hierarchical diffusion is when something spreads from a person or place of power and influence (figure 1.37). Geographers most often refer to hierarchical diffusion in terms of an urban hierarchy. If cities are ranked by population from large to small, it is more common for a new idea or item to originate in and diffuse to large cities first, then to medium-size cities, and later to small cities and towns. The latest musical trend or fashion typically begins in a large city, then diffuses to other large cities, even if they are far away—think New York, Los Angeles, London, and Paris. Medium-size cities will pick up on the trend a bit later, while diffusion to small towns will be later still.
In addition to urban hierarchies, diffusion can move along an income hierarchy, often from rich to poor. In most countries, the diffusion of things such as higher education, personal computers, and cars with airbags all began in households and neighborhoods with higher incomes. As time progressed, the cost of these innovations decreased, and they became more widely available in neighborhoods with lower income.
Stimulus diffusion is when a characteristic spreads to a new place, but rather than remaining in its original form, it stimulates a new innovation. For example, US fast-food restaurants have diffused around the world, but those that have been most successful have modified their menus to reflect local culture. For example, rather than a simple diffusion of burgers and fries to Japan, McDonald’s offers crab croquette burgers and fries with white and dark chocolate sauce. McDonald’s is a global company, but its diffusion worldwide has stimulated innovation in new menu items. In a similar sense, the idea behind ride-hailing services such as Uber has stimulated new services for hailing rickshaws in India.
Figure 1.37.Hierarchical diffusion of a hypothetical trend. Geographers often study hierarchical diffusion in terms of urban hierarchies. New trends and products originate in large cities, then diffuse to medium and small cities over time. Maps by author. Data sources: Esri, HERE, Garmin, NGA, USGS.
Diffusion processes do not flow unimpeded across the landscape but rather face barriers to diffusion. Barriers can be physical or cultural. Mountains, oceans, rivers, dense forests, and deserts can act as physical barriers that slow or stop diffusion. Physical barriers can also include walls, trenches, and other human-built features. Cultural barriers can be just as powerful in stopping or slowing diffusion. Language, race and ethnicity, religion, income, and other cultural differences can limit communication and interaction between groups of people, thus inhibiting the diffusion of ideas and items from one community to another, be it religion and philosophy, music, disease, or technology. Furthermore, cultures that are more conservative and tradition-based will resist the diffusion of new ideas and items from other people and places. The Taliban’s prohibition of modernity in terms of music, technology, clothing, and much more limits diffusion into areas under its control.
Go to ArcGIS Online to complete exercise 1.6: “Origin, spatial diffusion, and spatial interaction.”
Human–environment interaction
The ecological perspective: Cultural ecology
As discussed so far, we have seen how spatial patterns are created from the interaction between places and the diffusion of things over space. But these patterns are also the result of another type of relationship studied by geographers: human-environment interaction. The interaction between humans and the environment is known as the ecological perspective, or cultural ecology—the interplay of human cultures with ecological patterns.
Figure 1.38.Garbage-filled harbor in Malaysia. Humans’ actions often have a profound negative impact on the environment, threatening the health of people and wildlife alike. Photo by Rich Carey. Stock photo ID: 214284142. Shutterstock.
Humans impact the environment in many ways. They alter plant and wildlife distributions by converting natural habitats to farms and cities; they change the course of rivers through dams and canals; they alter the quality of air, water, and soils through pollution; and they remove hills and fill valleys for development projects (figure 1.38). Very few places are free of human impacts, and with human-induced climate change, the distributions of plants, animals, crops, and human settlements are likely to be further transformed at a global scale.
Similarly, the environment impacts humans. Human settlements tend to be less populous in areas that are too wet, such as the tropics; too dry, such as deserts; or too cold, such as the Far North and Far South (figure 1.39). These types of environments are poor for agriculture and make large-scale food production difficult, thus limiting human settlement. The natural environment also influences components of human culture. For example, due to climatic differences, northern Europeans have a traditional diet that is high in fish, meats, and carbohydrates, while Mediterranean Europeans have a traditional diet that includes a wide variety of fruits and vegetables. The way people dress, obviously, is also a function of environment; just envision people in sun-soaked Rio de Janeiro, Brazil, and chilly Helsinki, Finland. How people build varies as well, with wood used in forests, adobe in deserts, steeply pitched roofs in areas of heavy snowfall, and flat roofs in arid regions.
Environmental determinism and possibilism
Environmental determinism is the idea that the natural environment determines much of the spatial patterns of human activity. As in the earlier examples, the environment is seen as determining where people live or do not live, what types of crops they grow and what foods they eat, how they dress, and how they build their houses. This theory has also been used to explain patterns of economic development. European thinkers once believed that the mid-latitudes, which were not too hot, too cold, too wet, or too dry, led to vigorous, hard-working, and productive societies. In contrast, tropical latitudes, with their heat and humidity, made hard work so unpleasant that societies remained primitive. Environmental constraints on hard work were said to hold true of hot desert regions and cold high-latitude regions as well.
Figure 1.39.Ittoqqortoormiit Village in Greenland. Arctic settlements such as this village tend to have low populations due to harsh environmental conditions. Photo by Adwo. Stock photo ID: 200898014. Shutterstock.
Environmental determinism fell out of favor during the twentieth century. Historically, many successful societies have formed in areas once considered to have overly harsh environments, from the Mayans of Central America to the great ancient cities of Mesopotamia in the Middle East. More recently, tropical places such as Singapore and Hong Kong have become among the richest in the world, and major urban areas such as Phoenix and Las Vegas have grown in deserts. Irrigation allows for new crops in the desert, while fertilizers in the tropics can overcome poor soil quality. As is clear from these examples, environmental conditions do not directly determine the spatial patterns of human activity.
Instead, the concept of possibilism is more appropriately used when studying human-environment interaction. Possibilism is the notion that the natural environment creates possible outcomes for human activity but that humans can overcome many of the constraints imposed by nature. With human creativity, tropical Singapore used the natural conditions of a harbor located on trade routes between Asia, the Middle East, and Europe to become a wealthy state tied to international trade and services. Human taming of the Colorado River via
