Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Q: Fact 1: cutting down trees has a negative impact on an ecosystem. 
Fact 2: Ecosystems are living communities.

A: Cutting down trees has a negative impact on living communities.
****
Q: Fact 1: bacteria in soil convert atmospheric nitrogen into a form usable by plants. 
Fact 2: Plants have to have nitrogen to grow.

A: bacteria helps plants grow.
****
Q: Fact 1: Most people can survive only a few days without water. 
Fact 2: Water is made up of H2O molecules.

A:
Most people can survive only a few days without H2O.
****