Final answer:
The statement about Joshua trees dying due to global warming is a testable hypothesis which can be investigated through experiments or studies to confirm or refute the proposed causal relationship.
Step-by-step explanation:
The statement "Joshua trees are dying due to global warming" is a testable hypothesis. A hypothesis is a tentative explanation for scientific observations, one that formulates a system that can be tested through observation or experimentation.
This notion that Joshua trees are dying because of global warming proposes a causal relationship, which can be investigated to confirm if global warming is indeed the factor causing the death of Joshua trees. By analyzing data and perhaps conducting controlled experiments or observational studies, one could gather evidence to either support or refute this hypothesis.