A world of activities set for Earth Day.

Some people will bicycle along the beach, some will ride the waves on surfboards. Others will listen to environmental speakers or sweat a little planting trees and picking up trash.

But however they do it, all will be observing the global Earth Day 1990 today through Sunday .

Some organizers say that this Earth Day may be more critical than the original one 20 years ago because environmental problems--from global warming to vanishing rain forests--have worsened.

“We have a deep concern for the environment, and it’s not going to go away,” said Barbara Epstein, co-chair of the largest observance in the area--a free family festival that 18 organizations are sponsoring Sunday from 10 a.m. to 5 p.m. at Palos Verdes High School, 600 Cloyden Road, Palos Verdes Estates.

The Palos Verdes Symphonic Band will play, students will perform a musical drama and there will be live animals and ecology activities to entertain children. Environmentalist and “Ecotopia” author Ernest Callenbach will be the keynote speaker.

Torrance will observe Earth Day from 10 a.m. to 6 p.m. Sunday as part of the annual Friendship Festival in Old Downtown Torrance. Booths will be located on Cravens Avenue between El Prado and Post Avenue with information on conserving water and energy and preserving natural resources. There will be music, and speakers will talk about recycling and handling household wastes. Tours of the Madrona Marsh wetlands will be given.

Redondo Beach will have an Environmental Awareness Booth on the Redondo Pier at the foot of Torrance Boulevard on Sunday from noon to 5 p.m. Information will be distributed on water conservation, drought-tolerant plants and recycling.

The Cabrillo Marine Museum in San Pedro will focus on safeguarding the coastal environment Sunday from noon to 5 p.m. with films, guided tours of a man-made salt marsh near the museum and a hands-on Discovery Center. Admission to the museum--at 3720 Stephen White Drive--is free; parking is $4.

Beyond War, a nonprofit educational organization, will honor seventh- and eighth-grade environmental essay contest winners at an Earth Day banquet Sunday at 6 p.m. at the Riviera United Methodist Church, 375 Palos Verdes Blvd., Redondo Beach. The cost is $10; for reservations call 370-2140.

Bicyclists are invited to demonstrate pollution-free transportation by pedaling from the Redondo Pier to the Santa Monica Pier on Sunday. Cyclists will leave on the 20-mile ride--sponsored by the L.A. Wheelmen--from the north side of the pier at 9 a.m.

The King Harbor Sport Center and the Dapper Dan Surfing Assn. will co-sponsor a surfing contest at the Manhattan Beach Pier at the foot of Manhattan Beach Boulevard at 7 a.m. Sunday. The contest and a barbecue dinner from 5 to 7 p.m. that evening at the center will raise funds for Heal the Bay, an organization combatting sewage pollution in Santa Monica Bay.

Surfers will pay a $30 fee. Price of the dinner is $15 and includes dancing to a surf band. Admission after 7 p.m. is $10. The sports center is at 818 Harbor Drive, Redondo Beach.

Three cities will plant trees:

* Redondo Beach, where volunteers may call City Park Supt. Ken Dyer at 318-0687. He will direct them to a school where trees will be planted today from 9 a.m. to 5 p.m.

* Carson, on Saturday from 10 to 11 a.m. in the east parking lot of the Carson Community Center, 3 Civic Plaza, next to City Hall.

* Rancho Palos Verdes, where volunteers will meet Sunday at 8:30 a.m. at City Hall, 30940 Hawthorne Blvd. Trees will be planted at Hesse and Ladera Linda parks.

There will be cleanups in two communities:

* Hermosa Beach, where aluminum cans, newspapers and plastic soda bottles will be accepted for recycling on Saturday between 9 a.m. and 4 p.m. at Hermosa Valley School, 1645 Valley Drive. On Sunday, volunteers will pick up trash along the Hermosa Valley Green Belt, an old railroad right of way that runs along Valley Drive between north and south city limits. Volunteers will meet at the green belt and Pier Avenue at 10 a.m. and work until noon.

* The Unocal Refinery, 1660 W. Anaheim St., Wilmington, where people may dispose of dangerous materials for free Saturday from 9 a.m. to 3 p.m. Such things as paints, pesticides, motor oils and batteries will be accepted. But don’t bring explosives or ammunition.