The graph on the left shows the supply and consumption of forests when the consumption rate and population growth rate are both low. The graph on the right shows soil erosion under the same conditions. Which conclusion do the graphs support?

a
As consumption of lumber decreases, forest resources and soil erosion also decrease.
b
When forests are cut down faster than they can be replenished, soil erosion quickly increases.
c
As consumption of lumber increases, forest resources and soil erosion also increase.
d
When forests are cut down faster, they are replenished faster, and soil erosion is kept in check.