I was just discussing a similar concept with other educators! I work in a zoo setting and a lot of conversations end up being about extinction, habitat loss, and the mistreatment of animals.
We discussed how the problems can seem too grand and our actions too small. Even when we follow the problem with ways we can help, guests often feel guilty and take responsibility for not having done the sustainable actions prior. Overall, everyone feels discouraged.
As mentioned by Brooke, it is important to read your audience. Does this person care actually care? What is the age group? Will I lose their attention if I start mentioning something negative? What is their baseline knowledge of the concept? You can adjust your messaging based on their level of interest. It is OK to not hit everyone with the hard conservation messaging. If you develop their interest in the topic, they will begin to admire it and in turn, what to preserve it.
With all of the concepts we are messaging in EE, it is important to remind your students (and yourself) that there is still hope everywhere. Advancements and discoveries are constantly being made and we need to celebrate the little things! It is helpful to remind guests that there is always something they can do to help and their impact matters.