New Orleans: A case study in the resilience of nature

In August 2005, the city of New Orleans was hit by a devastating hurricane, dubbed Katrina, and a subsequent storm surge that destroyed much of the city and killed many of its residents.  The Lower Ninth Ward of New Orleans was one of the hardest hit areas of the city because it was the location of two breaks in the levee and is also at a lower elevation than less damaged neighborhoods.

The population of New Orleans reached its peak of 627,525 in 1960.  A year after Katrina, the city’s population had plummeted to about 200,000.  Six and one-half years later, the population is estimated to be 356,000. 

Neither the loss of population nor the return was spread evenly throughout the city.  The Lower Ninth Ward lost 75% of its population since 2000 because the damage was greatest there and its previous inhabitants did not have the resources to restore their properties.  For the same reasons, there are few services in the Lower Ninth Ward, such as a supermarket, or a police or fire station, making it a less attractive place to live.

The New York Times Magazine recently published a feature about the Lower Ninth Ward aptly entitled, “Jungleland.”  The article reports that nature has returned to the Lower Ninth Ward of New Orleans without the help of man and now resembles a dense jungle, more heavily populated by animals than people. 

Nature returns to the Lower Ninth Ward

The Lower Ninth Ward is a case study in the resilience of nature.  It is being intensively studied by ecologists as an example of how nature recovers from natural disasters, such as the volcanic eruption of Mount St. Helens and the earthquake and tsunami in Japan one year ago.  What all these disasters have in common is that they wiped the ecological slate clean.  Everything growing and living in these places was swept away to bare ground.

The Lower Ninth Ward was built on fertile ground because it was the repository of sediment from the Mississippi River for millennia before it was protected by levees and built upon.  This is also a part of the country that enjoys a warm climate and plenty of rain.  These factors undoubtedly contributed to the robust and rapid regrowth of vegetation in the Lower Ninth Ward.

The regrowth is almost entirely non-native.   Before the land was cleared for plantations in the mid-1700s the native vegetation was reeds and brambles along the river, hardwood forest behind the river, giving way to cypress and palmetto swamp in the interior.  “Today there are few species native to the land, other than several kinds of sedge and aquatic grass.  Only a handful of palm, live oak, and bald cypress survived the storm.” * 

The current vegetation is described as: “A variety of species, some exotic, have moved in, among them crepe myrtle, black willow, and golden rain trees laced with vines.  The undergrowth is a chaotic mix of weeds as high as basketball hoops, and flowering shrubs like lantana, oleander and oxalis.”     

Last fall, the city of New Orleans launched a new campaign to reclaim the Lower Ninth Ward.  The city engaged a crew to clear the vacant lots of trash and vegetation in an effort to make the neighborhood more attractive to potential homeowners and investors.  At the rate of 20 lots per day, it takes the crew three months to clear the vegetation.  Then they begin again, because within three months the vigorous vegetation has reclaimed the vacant lots.

Birds return to the Lower Ninth Ward

An ornithologist from the University of New Orleans visited the Lower Ninth Ward with the author of the Times article.  He was permitted to visit the area for the first time one month after the storm, when attempts to find residents who hadn’t survived the storm were considered complete.  At that time he reported complete silence.  There was no birdsong in the Lower Ninth Ward. 

The birds that were common before the storm, such as mourning doves and house sparrows, are slowly beginning to return in small numbers.  There was a significant increase in the population of raptors, such as hawks, falcons, and shrikes.  The ornithologist speculated that an increase in the rodent population was responsible for this increased population of raptors, which he described as “supernatural.” 

The ornithologist accompanying the journalist waded into thickets covering several vacant properties, “pishing” as birders do to attract the birds to them.  We will let the ornithologist speak for himself as he rapturously reports to the journalist the many birds he sees and hears:

“’’I’ve gone whole winters without seeing a field sparrow in the New Orleans vicinity.  Field sparrows, swamp sparrows, simply do not winter in residential New Orleans…Orange-crowned warbler!’ He shouted back at me. ‘Ruby-crowned kinglet!’”

The journalist following the ornithologist couldn’t keep up:  “It was no longer possible to distinguish which calls were his and which the birds’.  He walked around a stand of 15-foot Chinese tallow trees, the green and crimson leaves waving mournfully in the wind.  And then he was gone.  The wilderness just swallowed him up.”   

Lessons learned in New Orleans

The recovery of nature in New Orleans is an ecological experiment that was not fabricated by scientists. Man did not manipulate the outcome.  And this is what nature is telling us:

• Native plants do not magically return when existing vegetation is wiped clean to bare ground
• Birds do not care if the vegetation is native or non-native.  They will inhabit either.
• Since the diet of many birds is predominantly insects, we should assume that the insects have also returned to the Lower Ninth Ward and that they are feeding on non-native vegetation.

* Nathaniel Rich, “Jungleland,” New York Times Magazine, March 25, 2012.  All quotes from this article