The pollutants disperse easily across wide geographic areas, retain their toxicity, and have a tendency to accumulate in the fatty tissues of organisms.
Whereas purposeful men could make their way across a narrow bridge, the slow diffusion of plant and animals would require an avenue as a continent and available for ages at a stretch.
Over the last 12 months, U.S. unemployment has jumped by more than a percentage point as the nation weathered a deepening recession that has spread around the world.