Every time someone builds a dream home in the country and landscapes with plants purchased from a big-box store, they’re carrying the newest wave of foreign invades into our so-called natural environments.  In one clever study performed in Germany, plant seeds were collected in one-way highway tunnels in wich the traffic were either leaving or entering the city of Berlin.  The seeds were being carried on the surfaces of the vehicles, and some blew off and fell into the traps as the vehicles were passing through the tunnels.  More seeds were leaving the city of Berlin than entering.  The city had become a net exporter of seeds, especially the seeds of introduced species.

We’re not at the forefront of the movement to welcome nature back into our cities.  I’m happy to acknowledge the outstanding work taking place elsewhere.  We need to do what is manifestly good for us.  Even that is not easy.  It can still be accomplished by wisely managing the cultural evolutionary process.  The world with us can be a garden of Eden, as soon as we decide to end our self-imposed exile.

David Sloan Wilson, The Neighborhood Project (2011) pp 263, 271