“We have snakes,” Mary Brock said. “Long, thick snakes. Kingsnakes, rattlesnakes.”

Brock was walking Pee Wee, a small, high-strung West Highland terrier who darted into the brush at the slightest provocation — a sudden breeze, shifting gravel, a tour bus rumbling down Caffin Avenue several blocks east. But Pee Wee had reason to be anxious. Brock was anxious. Most residents of the Lower Ninth Ward in New Orleans are anxious. “A lot of people in my little area died after Katrina,” Brock said. “Because of too much stress.” The most immediate sources of stress that October morning were the stray Rottweilers. Brock had seen packs of them in the wildly overgrown lots, prowling for food. Pee Wee, it seemed, had seen them, too. “I know they used to be pets because they are beautiful animals.” Brock corrected herself: “They were beautiful animals. When I first saw them, they were nice and clean — inside-the-house animals. But now they just look sad.”

The Lower Ninth has become a dumping ground for unwanted dogs and cats. People from all over the city take the Claiborne Avenue Bridge over the Industrial Canal, bounce along the fractured streets until they reach a suitably empty area and then toss the animals out of the car. But it’s not just pets. The neighborhood has become a dumping ground for many kinds of unwanted things. Contractors, rather than drive to the city dump in New Orleans East, sweep trailers full of construction debris onto the street. Auto shops, rather than pay the tire-disposal fee ($2 a tire), dump tires by the dozen. The tire problem has become so desperate that the city is debating changes to the law. (One humble suggestion: a $2 reward per tire.) You also see burned piles of household garbage, cotton-candy-pink tufts of insulation foam, turquoise PVC pipes, sodden couches tumescing like sea sponges and abandoned cars. Sometimes the cars contain bodies. In August, the police discovered an incinerated corpse in a white Dodge Charger that was left in the middle of an abandoned lot near the intersection of Choctaw and Law, two blocks from where Mary Brock was walking Pee Wee. Nobody knew how long the car had been there; it was concealed from the closest house, half a block away, by 12-foot-high grass. That entire stretch of Choctaw Street, for that matter, was no longer visible. It had been devoured by forest. Every housing plot on both sides of the street for two blocks, between Rocheblave and Law, was abandoned. Through the weeds, you could just make out a cross marking the spot where Brock’s neighbor had drowned.

It is misleading to talk about abandoned lots in the context of the Lower Ninth Ward. Vast sections of the neighborhood have been abandoned, so it’s often unclear where one property ends and the next begins. (An exception is the sliver of land on the neighborhood’s innermost edge, where Brad Pitt’s Make It Right Foundation has built 76 solar-paneled, pastel-hued homes — though this seems less a part of the neighborhood than a Special Economic Zone.) To visualize how the Lower Ninth looked in September — before the city’s most recent campaign to reclaim the neighborhood — you have to understand that it no longer resembled an urban, or even suburban environment. Where once there stood orderly rows of single-family homes with driveways and front yards, there was jungle. The vegetation had all sprouted since Katrina. Trees that did not exist before the storm are now 30 feet high.

The cartoonish pace of vegetation growth resembles something out of a Chia Pet commercial, but it is hardly surprising to New Orleanians long accustomed to roads warped by tree roots and yards invaded by weeds. The soil in the Lower Ninth is extraordinarily fertile, thanks to centuries of alluvial deposits from the Mississippi River, which forms the neighborhood’s southern boundary. From the river, the neighborhood descends, like a long ramp, down to an open-water, brackish marsh called Bayou Bienvenue. This back part of the neighborhood, which, at its lowest point, is four feet below sea level, was the most devastated by the storm and remains the least inhabited. Its population has decreased by 85 percent since 2000.