The following comment was submitted by "cattus-runner" and was accidently deleted -- it has also been added to the Cattus Island Park page.
The Cooper Environmental Center is now back open (as of Spring 2017), as well as the orange trail that goes around the island (unofficially known as "Scout Island" in honor of the Boy Scouts who volunteered to build the trail). Instead of following the main path north to the blue trail, one can also go directly across the main path from the Cooper Environmental Center onto the red trail, which connects to the yellow trail, leading visitors to sand dunes and much more dense and secluded paths. The red trail can also be picked up 100 feet southeast of the playground near the parking lot. Looping through all of the trails (red, red/white, yellow, blue, blue/white, orange) and the entire main path, my journeys come out to about 10 miles, with little to no elevation. Ticks can be a problem, and during the hottest summer months the shadiest parts of the trails can become both muggy and buggy. I think it is worth it for the amount of nature that you're exposed to here. I have seen ospreys, deer, egrets, foxes, turkeys, bald eagles, and much more. Many visitors to the park appear to stick to the main path without jutting off to the side trails (especially the red and yellow trails) and are missing out on exploring all of Cattus. I walk, run, and bike in this park at least three times a week and am very thankful for its preservation.