Erosion from rising sea levels could cost California hundreds of millions of dollars in lost tourism and tax revenue as beaches shrink and buildings require additional protection, according to a state-commissioned study.

As climate change causes the ocean to warm and expands, San Francisco State University economists predict increased storm damage and erosion will likely narrow California's beaches and diminish their appeal to tourists and wildlife.

You need a certain amount of space for people to recreate, and, as beaches erode, you lose beach-size and you lose tourism, said Philip King, an associate economics professor at the university and an author of the study.

Commissioned by the California Department of Boating and Waterways, the study focused on five California beach communities beginning with San Diego in the south, Los Angeles' Venice Beach, two seafront areas in Malibu, and San Francisco's Ocean Beach.

The researchers used three sea-level-rise scenarios to make their predictions: a rise of three feet, a rise of 4.5 feet, and a rise of 6.5 feet. By using sea-level-rise projections, the group estimated the economic loss from flooding and beach erosion.

For example: a rise of 4.5 feet by 2100 could cost Venice Beach up to $440 million in tourism and other revenue, according to the study. That number could reach nearly $500 million up the coast in Malibu's Zuma and Broad Beaches.

The authors acknowledge that coastal storms and beach erosion are common events that have shaped the geography of coastal environments since the beginning of time. However, because sea levels are projected to rise at much faster rates and storms are expected to be more intense due to a warming planet, the effects over the next century are predicted to be greater than ever.

The economic risks in this report, presented conservatively, demonstrate the scale and importance of sea-level-rise impacts in a local planning context, the report states. Sea-level rise is here and we need to start planning for it.

The report finds that beach erosion will also destroy large tracts of animal habitat.

More than 80 percent of Californians live in coastal communities, and California's beaches support local economies and critical natural species, King notes in the study.

The researchers hope that their findings will guide policymakers as they consider future oceanfront development.

The ocean has risen nearly eight inches in the past century. That number is expected to be dramatically higher over the coming decades.