If you’ve ever had a medical check-up, did you wonder why they put a cuff around your forearm, gave it a squeeze, and made you sit still and quiet? Or why they asked you to open your mouth so they could stick a thermometer under your tongue? Or put that cold stethoscope against your chest while you took deep breaths followed by sticking a clothespin thingamabob on your finger? What’s up with all the gizmos and gadgets and why all the bother?

What’s up is that all of these instruments measure the conditions of some of the most important, life-supporting functions, or vital signs, which keep your carcass from becoming, well, a carcass. The squeezy cuff is reading your blood pressure, which indicates how strongly your blood is pumping through your pipes. The thermometer measures your core body temperature, which affects many chemical reactions in your body that supply energy for your cells. With a stethoscope, the swooshing sound of air moving in and out of your lungs can be listened to. And the clothespin doohickey tracks the amount of oxygen being carried by your blood. Vital signs are critical indicators of your body’s overall health. By tracking them as you grow and mature, these measurements can be used as a guide or reference point for when your body isn’t feeling all that great.

Now what does your blood pressure have to do with US National Parks? While human vital signs are important in evaluating your body’s health, ecological vital signs are indicators for measuring ecosystem health. An ecosystem is a community of living organisms like frogs, trees, or bacteria, and nonliving materials such as water, dirt, and rocks that are located together and interact on some level. In a healthy ecosystem, all of the living and nonliving members exist in a state of natural balance in harmony with their environment. When something new enters the community, say a strange weed or insect, or something in the environment shifts, such as the air temperature becoming warmer, the health of the ecosystem can be threatened. Monitoring ecological vital signs gives scientists a reference point or baseline of the natural condition and alerts them when there is a change. While a healthy ecosystem can continue to support all its members and adapt to change, sometimes changes are too great and members of the ecosystem become stressed and have a hard time keeping up.

Although US National Parks are some of the most protected areas on the planet, the ecological health of many of these carefully safeguarded lands is increasingly uncertain due to our rapidly changing global environment. Here we present a collection of articles about how we study and understand the health of park ecosystems by measuring and tracking the condition of ecological vital signs. This scientific data helps park managers protect the valued resources of our parks and lessen harmful impacts when change is inevitable.