Much like people, many plants and wildlife have survived the disaster, and can be found throughout the ruins. Although nobody recognises or remembers any of them from prior to the disaster, more has been learnt over the months you do recall.
There are more plants and animals out there, beyond the limits of monument, there are probably more in monument. Rumours of animal attacks, that don't fit any of those you know, or glimpses of creatures in the distance. This page shows only the most common and well known, and is by no means an exhaustive list.

Either the disaster seems to have killed most of the plants growing through the city, or not many grew in it in the first place. Now shoots reach for the sky between cracks in the streets, and bare earth blooms. Here are notable plants that have been found:

Four leaves topping a long purple stalk, those foolish enough (or desperate enough) to eat them discovered that they are quite poisonous, causing swelling that will on occasion lead to death. Their roots come in a variety of colours, and spiral downwards, making them difficult to pull out. There are rumours that the roots are edible.

Large leafy herbs that seem to grow everywhere, even on metal beams. Those who have managed to locate makeshift pots have found they make good soup, if you can spare the firewood.

Layers of leafy crowns give this plant its name, which seems to prefer growing at the northern and eastern edges of the city. They have starchy seeds in the centre, which are edible when boiled.

Short stemmed, cerulean flowers with a very powerful, calming scent. Quite popular as a stress reliever. They're a bit rare, though, and mostly located near the old city.

While the plants are growing back, animals seem to be coming out of their hiding spots, or perhaps migrating from outside the city. Here are some of the notable wildlife:

Six legged furred predators with long legs and tails. Their fur ranges from midnight blue to abyssal black, and is very soft. They seem to be friendly, and most will allow you to pet them (but only on their terms!) and some even seem to have claimed certain people as theirs, bringing them small dead things. Word on the streets is that they have retractable claws. They are about a quarter meter in height and half a meter in length, and those who have killed some report they taste bad. They also complain that the others are now hostile to them…

Small, hunched, humanoid creatures with oversized ears and noses. They can sometimes be seen eating corpses, but are quite wary of (living) people, and generally unappetising. Despite their vague similarity to yourself, they do not seem to be intelligent.

Fluffy quadrapedal herbivore that seems to have no trouble eating the poisonous leaves and stalks, as well as the edible ones. They are fast, very skittish, and covered in soft white fur. They taste pretty good. They are about half a meter tall and half as much again long, with short rounded ears and tails. They have fairly flat faces, with a cute naked nose poking out a bit.

When a particularly irritated survivor tried calling them “flying nuisances”, they stumbled over their words and gave them a new name, which others found amusing so it stuck. These scaled nightmares fly around making a pest of themselves, raiding the reserves and other supply stores found around the ruins. They are too small to actually harm people, but show no fear in flying at people to make them drop their food. Vengeance is at hand, though - they taste delicious.
They have claws on their large, scaly wings and have short tails and toothless beaks. They tend to hang onto walls with their wing-claws and kick off of them with their back legs, which have a pair of forward facing claws and a single backward claw.

Four legged carnivores, about 20cm in height and 70cm in length (about a third of which is tail), they are covered in armoured segments, with each one overlapping the one behind it. They have sharp, crescent moon outcrops of armour pointing forward from the front segment, above the eyes, and the tail ends with two segments pointing backwards from it, looking like another crescent. They seem to have a very good sense of smell, and are good at digging around, using the frontal crescents to dig up debris in search of food. They have been known to attack people for their food (although they are easily outpaced, or just kicked away until they give up), leading to several injuries. Their bellies are unarmoured, and their claws are unimpressive.