Put in with conservationist Don Greene during todays Buffalo Bayou Canoe Tripfor a half-day flotilla. Greene will play tour guide and explain the urban ecosystem that has developed around the bayou, pointing out ways that you can help preserve its delicate balance. Theres a pre-trip meeting today at 7 p.m. at the Houston Arboretum and Nature Center. The canoe trip is at 1 p.m. Wednesday, January 17, with a starting point near the 610 Bridge and Woodway. For information, call 713-366-0379 or visit www.houstonarboretum.org. $85 to $105.