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.

Fact 1: cutting down trees has a negative impact on an ecosystem. 
Fact 2: An ecosystem can be in a desert, a tropical jungle, an ocean or a pond.
cutting down trees has a negative impact on a jungle.

Fact 1: Viruses contain DNA but not much else. 
Fact 2: DNA is encoded information.
viruses contain encoded information but not much else.

Fact 1: phase changes do not change mass. 
Fact 2: Melting is a phase change.

Mass does not change during melting.