EXPLORATION: Humans and Environmental Issues

1. Urban Threats

Urbanization spurs a unique set of issues to both humans and animals.

The promise of jobs and prosperity, among other factors, pulls people to cities. Half of the global population already lives in cities, and by 2050 two-thirds of the world's people are expected to live in urban areas. But in cities two of the most pressing problems facing the world today also come together: poverty and environmental degradation.

Poor air and water quality, insufficient water availability, waste-disposal problems, and high energy consumption are exacerbated by the increasing population density and demands of urban environments. Strong city planning will be essential in managing these and other difficulties as the world's urban areas swell.

Threats

• Intensive urban growth can lead to greater poverty, with local governments unable to provide services for all people.
• Concentrated energy use leads to greater air pollution with significant impact on human health.
• Automobile exhaust produces elevated lead levels in urban air.
• Large volumes of uncollected waste create multiple health hazards.
• Urban development can magnify the risk of environmental hazards such as flash flooding.
• Pollution and physical barriers to root growth promote loss of urban tree cover.
• Animal populations are inhibited by toxic substances, vehicles, and the loss of habitat and food sources.

Solutions

• Combat poverty by promoting economic development and job creation.
• Involve local community in local government.
• Reduce air pollution by upgrading energy use and alternative transport systems.
• Create private-public partnerships to provide services such as waste disposal and housing.
• Plant trees and incorporate the care of city green spaces as a key element in urban planning.

2. Population Pressure

This map shows global population dynamics over two scales. The first indicates national rates of migration from rural areas to cities from 1990 projected to 2050. The second, indicated by circles represents the population size of individual cities and their rate of growth from 1990 projected to 2030. Essentially, this map shows the global phenomenon of migration to cities and registers the intensity of that migration.

In 2015 the global population was circa 7.3 billion people. The United Nations forecasts that this will grow to 8.5 billion by 2030, 9.7 billion by 2050, and anywhere up to 13.3 billion by 2100.

With the need to source energy, food, water, and housing for so many additional people this century is likely to see competition for resources between people and between species take place on a scale not previously experienced. On the contrary, as pressure increases in the developing world, much of Europe is now experiencing shrinking population. Whether these nations can or should help relieve pressure in other parts of the world by opening their borders or boosting their immigration quotas is complicated.

The UN reports that there is a 23% chance that global population will stabilize or fall before 2100. This would bring to an end a growth cycle which began when a global population of circa four million nomads started to transition into settlements with the birth of the agricultural revolution.

3. Dams

Human beings have been blocking and harnessed rivers for a variety of purposes over hundreds of years. Those purposes include irrigation, flood control and water storage. In the past hundred years or so, large dams have been built for the exclusive purpose of generation hydropower. In fact, in British Columbia, most of our electricity comes from hydroelectric dams. 

While dams can benefit society, they also cause considerable harm to rivers. Dams have flooded huge valleys displacing both people and wildlife, depleted fisheries, and degraded river ecosystems.

FOUR WAYS DAMS DAMAGE RIVERS

1. DAMS BLOCK RIVERS AND FLOOD LARGE AREAS

   Dams flood large areas, usually valleys. This can lead to habitat loss for untold numbers of species. 

   Dams prevent fish migration. This limits their ability to access spawning habitat, seek out food resources, and escape predation. Fish passage structures can enable a percentage of fish to pass around a dam, but their effectiveness decreases depending on the species of fish and the number of dams fish have to traverse.

2. DAMS SLOW RIVERS

   Aquatic organisms, including fish such as salmon and river herring, depend on steady flows to guide them.

   Stagnant reservoir pools disorient migrating fish and can significantly increase the duration of their migration.

   Dams can also alter the timing of flows. Some hydropower dams, for example, withhold and then release water to generate power for peak demand periods.

   These irregular releases destroy natural seasonal flow variations that trigger natural growth and reproduction cycles in many species.

3. DAMS ALTER HABITAT

   Dams change the way rivers function. They can trap sediment, burying rock riverbeds where fish spawn.

   Gravel, logs, and other important food and habitat features can also become trapped behind dams. This negatively affects the creation and maintenance of more complex habitat downstream.

   Dams that divert water for power and other uses also remove water needed for healthy in-stream ecosystems. Peaking power operations can cause dramatic changes in reservoir water levels. This can leave stretches below dams completely de-watered.

4. DAMS IMPACT WATER QUALITY

   Slow-moving or still reservoirs can heat up, resulting in abnormal temperature fluctuations which can affect sensitive species. This can lead to algal blooms and decreased oxygen levels.

   Other dams decrease temperatures by releasing cooled, oxygen-deprived water from the reservoir bottom.