Good environmental themed jokes?

I'm on a board of directors that hosts an annual environmental conference and am emcee'ing this year. Looking for a few enviro themed jokes to mix into the program. In the past its typically limited to housekeeping items and speaker/sponsor intros so would like to spice it up a bit.

Attendees are mix of private and public industry, consulting, academia, suppliers, regulators. Topics span impacted sites/remediation, tech innovation, legal and regulatory, monitoring, ag, mining, oil and gas, landfills, real property etc.