Scientists predict that the level of ozone depleting chemicals found in stratosphere will decline in the next 2-4 years. This prediction is based upon several pieces of information. Since the Montreal Protocol we have seen a decline in the amount of ozone depleting chemicals in the troposphere. When the information about the length of time it takes for ozone depleting chemical to move from the troposphere to the stratosphere are combined with the information about the quantity of ozone depleting chemicals in the troposphere, we are able to estimate that the levels of ozone depleting chemicals will begin to decline in the stratosphere sometimes within the next 2-4 years. Mutualism is a relationship that exists between species.
Mutualism is a form of cooperation.
If humans did not need organisms to consume the dead skin on our skin, the organisms who perform this task would not exist. Diversity would be less if mutualistic relationships between organisms did not exist. To explain the process in a simplistic manner, if one organism in the second trophic level is to be supported, then 10 organisms are needed in the first trophic level. The island ecosystem is more susceptivel to large changes in its ecosystem if a non-native species is introduced because an island ecosystem is simplier than an ecosystem found on a continent. Those ecosystems with less diversity are less able to maintain a dynamic balance.