The End of the World?

She walked down the street, gazing about at the ruins surrounding her. Ruins and dust, that was all that was left now, since the ancient humans destroyed the Earth.
She had heard stories about animals; bears, wolves, tigers; beautiful, bright, wild creatures of the past. Plants too, radiant blues, pinks, oranges and reds. Plants that could create oxygen, plants that ate bugs. All imaginary fantasies now.
A loud chomping noise woke her from her daydream. Rats. The only animal left. They were not your ordinary rats, but giant beasts, evolving into huge, terrifying monsters.
The streetlight buzzed, flickered, then went out. She hurried home to a small "box", one of many others on the block. She hated her apartment, a small dreary room, with mildew and the rats as her only companions.
She ate her dinner, small tins of ham and peas, the only food left. She went to bed, not being able to sleep or do anything else.
She woke up to a loud knocking on her door. She jumped out of bed and quickly answered it. A stranger, unshaven and wearing an odd suit greeted her. "Hurry. We found a plant!" he whispered with urgency, "It won't last long!"
They quietly rushed out of the apartment building. In the cool morning haze, she saw others quietly walking toward something. It was as if they were all driven toward the Mecca of days past.
They all arrived at the same time, about 50 people all driven toward the light of the flower. "It's a sunflower," explains an elderly and decrepit lady. They all gather around the flower, in awe of the simplistic beauty of it.
The sun starts to rise. Quickly they regroup around the mysterious elderly lady, and she gravely hands one seed to each of them.
"Protect them with your lives," she makes them solemnly swear. After they receive their seeds, they pause, look at the sunflower once more, then disappear into the alleys as quickly as the retreating darkness.
She is amazed that they would entrust her with a seed, a precious reminder of the past, a vial of the future.
She hurries home. Her decision is made. She is leaving this place, this chasm of dust, darkness and despair. She will make her way to a fabled place, a land where the animals still roam and plants are everywhere. She rushes home to pack.
"Hey, you! What are you doing?" someone shouts. She starts to run, running as fast as she can. The seed must be protected.