Human Population Growth and Urban Wildlands

As the growing human population reaches further and further into remote areas in search of room to build cities, housing developments, golf courses, and new farms, it is squeezing wildlife into ever smaller habitat refuges. For endangered species like the green sea turtle, Mississippi gopher frog, cactus ferruginous pygmy owl, Alabama beach mouse and California condor, there is often nowhere else to go when the developments march in. These species and many others are in danger of following the Lake Sammamish kokanee salmon into extinction. The kokanee steadily declined as Seattle sprawled eastward, polluting its water and destroying its spawning habitat. It went extinct in 2001. And the most recent review of the northern red-bellied cooter — a turtle that can only be found in a few Massachusetts ponds — explicitly deems the species still endangered due, in part, to encroachment of residential growth and human demand for water.

Case Study: Florida Panther on the Brink

The Florida panther once roamed over much of the southeastern United States, but now only about 100 individuals remain in just 5 percent of the species’ historic range. Panther numbers are so low that the population has suffered from inbreeding depression. Only a cross-breeding program with cougars from Texas has provided a reprieve from certain extinction. [1]

While the panther’s numbers have plummeted over the past 30 years, Florida’s human population nearly doubled. As the coasts become fully developed and unaffordable, Florida development is increasingly moving inland, where it comes into direct conflict with panthers. The five counties that contain the last remaining panther population are projected to grow another 55 percent in the next 30 years.

This unsustainable growth has made car collisions the primary cause of panther death, followed by males killing each other in competition for insufficient space in which to establish territories that can be as large as 200 square miles. [1]

It is far from clear that the panther will survive as its remaining habitat shrinks each year, encroached upon on all sides by urban and agricultural expansion. According to the U.S. National Park Service, “The odds for the long-term survival of the Florida panther in the wild are not good. The human population in the region continues to increase, resulting in urban growth and expansion of the regional highway network into former panther habitat…Any action that decreases the wilderness qualities of the Everglades region impacts this species. The existing threats to the panther are interrelated and cannot be separated. The primary threat to the Florida panther has been human encroachment into panther habitat.” [2]

A recent scientific study concluded that the current area of primary habitat “provides just enough space to support a population that is barely viable demographically as long as the habitat base remains stable.” Unfortunately, the habitat is anything but stable. The study notes that 27 percent of the panther’s primary habitat in southwest Florida is privately owned, much of which is slated for developments such as Big Cypress, a proposed city of 9,000 homes on 2,800 acres. Areas targeted for development include a crucial dispersal corridor that could provide panthers an outlet to recolonize potential habitat to the north. The study concludes that the Florida panther will need at least “three self-sustaining populations” totaling at least 300 individuals, with movement corridors connecting them, if it is to achieve genetic stability and recover. [1]

Wetland Losses

Destruction of wetlands is a major threat to the panther and is associated with road construction and urban development across the lower 48 states. Between the 1780s and 1980s, more than half of the wetlands in the continental United States were lost to dredging, filling, channelization, dams, and other aspects of rural and urban development. About half of Florida’s wetlands have been destroyed. Some states, such as California and Ohio, have lost over 90 percent of their wetlands.

Recent efforts to highlight the value of these ecologically important and biodiverse areas have resulted in wetlands creation and restoration efforts that have helped to stem the tide of net loss. But according to the U.S. Fish and Wildlife Service, tens of thousands of acres of intact wetlands are still destroyed every year, almost two-thirds of that area by “urban expansion and rural development,” a dynamic that is “particularly evident” in Florida. Additionally, many wetlands that persist are significantly degraded through contamination by pollution from urban and agricultural runoff. [3]

Water Supplies Stretched to the Breaking Point

Globally, humans now use almost two-thirds of all freshwater runoff. In many places, population growth is outstripping water availability, destabilizing water-delivery systems and causing crises. The United States is not immune to such crises, particularly in urban communities in rapidly growing areas such as the Southwest and South. The residents of Atlanta were alarmed in recent years as Lake Lanier reservoir, the foundation of their water supply, repeatedly shrank to historic lows in the midst of protracted drought.

Some observers speculated that changes in precipitation patterns due to global warming may have led to the water shortage in Georgia. Others blamed the environmental needs of downstream ecosystems, including endangered aquatic species. But a recent study by Columbia University climate experts showed that the drought that triggered the shortage was not unprecedented, but in fact a “typical event.” The researchers concluded that “the root of the water supply problem in the Southeast is a growing population….” Between 1990 and 2007, Georgia’s population exploded from 6.5 million to 9.5 million, a leap of nearly 50 percent in just 17 years. [4]

In short, a dramatically increased population now relies on the same limited supply of available water. “The problem is, in the last 10 years population has grown phenomenally, and hardly anyone, including the politicians, has been paying any attention,” observed lead author Richard Seager. “It was a lot drier in the 19th century than it has been recently, but there were so few people around, it didn't harm anyone,” said Seager. “Now, we are building big urban centers that make us vulnerable to even slight downturns.” [5]

An even more ominous predicament looms over the Colorado River, which supplies water to 30 million people and vast agricultural production in seven states and northwestern Mexico. It is already overallocated and suffering from 10 years of drought. Climate change models predict a decline of available water between 6 percent to 40 percent by 2050, while the number of people relying on it may double. The booming city of Las Vegas is desperately looking for schemes to enable its continued unsustainable growth, including proposals to pipe in groundwater from hundreds of miles away.

As rapidly growing urban populations seek to augment water supplies rather than control their growth, they come into conflict with the ecosystem needs of other species, triggering lawsuits, water shortages, and rationing. In the face of dire predictions based on new research that has revised and improved our understanding of the hydrological cycle in the Colorado River basin, one Arizona water expert remarked, “The future ain’t what it used to be.” Another observed, “In the West, it’s pretty much uncharted territory once you move closer to that abyss of not enough water.” [6]

Killing Roads

A particularly destructive effect of urban sprawl is the scourge of road construction and vehicular traffic. Florida panthers are just one of thousands of species being killed in significant numbers each year by car collisions. Comprehensive data is lacking, but estimates suggest that somewhere between 500,000 and one million vertebrates are killed in collisions with vehicles on U.S. roads each day, along with untold numbers of invertebrates. Additional mortality is caused by road construction, which often buries animals alive. Roads also block movement corridors and disrupt foraging and migration patterns, while vehicle traffic contributes to the spread of exotic species and the contamination of air, soil and waterways from runoff. Such pernicious effects are compounded by the vicious circle of road construction spurring further development far from urban cores.

The Growth-Consumption Spiral Must be Overcome

Water wars notwithstanding, habitat loss and fragmentation, much of it due to urban sprawl, remains the biggest immediate threat to imperiled species in the United States. Consumption and development patterns exacerbate population growth, with the size and footprint of new homes rapidly increasing and fewer people living in each home. Second home ownership increased by 17 percent between 1999 and 2005, further compounding the impact of each new homeowner that enters the market. Such rapacious consumption patterns result in a land conversion rate twice that of population growth, making urban sprawl the most predominant form of land use change in the nation. [7]

Surprisingly, the state of Florida’s population actually shrank slightly between 2008 and 2009, largely due to economic recession and fewer people moving into the state. But the reaction of alarmed pundits and panicked politicians to a 0.3 percent contraction in population does not bode well for the future. In a state where the prevailing growth-for-its-own-sake mentality earned it the nickname of “the Ponzi State,” leaders are now scrambling for ways to crank up a rebound as soon as possible. One demographer called it “a real psychological blow,” and observed, “I don’t know if you can take a whole state to a psychiatrist, but the whole Florida economy was based on migration flows.” [8]

As long as population growth and increased consumption levels are viewed as inherently positive, states like Florida will continue to destroy their natural heritage in the quest to keep the human population Ponzi scheme from collapsing. The result will be devastating to communities seeking a sustainable balance and catastrophic for endangered species such as the Florida panther, which are being squeezed ever closer to extinction.


  1. Kautz, R., et al. 2006. How Much Is Enough? Landscape-scale Conservation for the Florida Panther. Biological Conservation, 130 (2006) 118-133.
  2. U.S. National Park Service. 1994. Assessment of Big Cypress I-75 Recreational Access Plan, January, 1994.
  3. Dahl, T.E. 2006. Status and Trends of Wetlands in the Conterminous Untied States, 1998-2004. U.S. Department of Interior, Fish and Wildlife Service.
  4. Seager, R., A. Tzanova, J. Nakamura. 2009. Drought in the Southeastern United States: Causes, Variability Over the Last Millenium, and the Potential for Future Hydroclimate Change. Journal of Climate, Vol. 22, 5021-5045.
  5. Environment News Service, October 20, 2009. Southeast Water Scarcity Blamed on Human Population, Not Climate.
  6. Beal, T. 2009. Arizona’s Water Future Is Cloudy, Worried Experts Agree. Arizona Daily Star, September 24, 2009.
  7. Markham, V.D., Center for Environment and Population. 2009. U.S. Population, Energy, and Climate Change.
  8. Cave, D. 2009. After Century of Growth, Tide Turns in Florida. New York Times, August 29, 2009


Banner photo collage credits: Development courtesy Flickr/Capt' Gorgeous; hiking child courtesy Flickr/Trevor Manternach. Ribbon seal by Dr. Peter Boveng, NOAA; Sandplain Gerardia courtesy USFWS; Orca courtesy NOAA.