A．Too many animals eating the plants in one small area.
B．Planting too much vegetation in one small area.
C．Too many people building houses in one small area.
D．Bringing together the wrong kinds of animals and plants.
A．The animals overfertilize the soil.
B．Dead plant roots can't hold the soil together.
C．The wrong types of plants are left standing.
D．There is a buildup of plant and animal matter.
A．It can cause flooding
B．It can carry diseases that affect animals.
C．It can introduce too much salt into the soil.
D．It can divert water from important crops.