Your health and wellbeing and that of the environment can be directly and indirectly linked, for example:
Direct: spending time in nature is good for your physical and mental health
Indirect: if being in nature makes you appreciate and care more about it you're more likely to try to protect it
Both: if you walk or cycle instead of driving you're being active and creating less air pollution
A polluted environment and climate susceptible to extreme weather events is detrimental to human health.
A healthy diet (including plenty of fruit, vegetables and nuts, and limited processed meat) has been shown in a late 2018 research article to reduce the risk of depression. This also equates to a low carbon footprint diet.
In Southampton I have created a nature and biodiversity hub and a health and wellbeing hub that anyone can join - get in touch if you would like to. They have separate aims but also have important crossovers.
Thinking about Maslow's hierarchy of needs, people have to satisfy their basic needs, which include health and wellbeing, before being able to focus on other concerns like their environmental impact. So in addition to the direct links mentioned, helping people to be healthy is also a prerequisite for them to take environmental action!
Good health and wellbeing are valuable in their own right and contribute to happiness. Here are some actions you can take that research shows lead to improved happiness. Consider challenging yourself to try one or two of them.