Yes, a summer vacation is getting more expensive. Airfares have gone up. The cost of driving anywhere is more than $4 a gallon and climbing.

But there's still one thing that's free: our beautiful public beaches. And with summer officially here, we can expect more people to choose this inexpensive recreational option.

That's why the most recent release of the Ocean Conservancy's International Coastal Cleanup survey continues to be an important reminder to keep our beaches beautiful.

In Hawai'i, volunteers picked up more than 163,000 pieces of trash on beaches statewide in a single day in 2007. And that day was in September, presumably when the beaches were less crowded.

Most of these pieces picked up were the usual suspects: food containers, bottles, caps. The trash leader is cigarette butts — little, slow-to-degrade pellets of pollution containing chemicals such as lead, cadmium and arsenic. More than 72,000 pieces were collected.

Like those tiny pieces of plastic trash floating at sea, these small bits, which can be easily put in a trash can, are instead easily ingested by wildlife, poisoning them.

This isn't trivial. More than 1 million seabirds and 100,000 marine mammals are killed each year because of trash in the ocean, according to the Ocean Conservancy.

If this is not reason enough to put our 'opala where it belongs, consider this: On that September day, it took 3,056 volunteers to pick up the 45,568 pounds of trash over much of the 87 miles of Hawai'i's coastline.

Some of that trash, of course, was washed ashore after being dumped at sea.

But most beach trash comes from those who use it — namely, us. And since we don't have thousands of volunteers to clean up after us every weekend, it's imperative that we do it ourselves.

In Hawai'i, our beaches are not just a place to spend a sunny day; they are a natural resource, as valuable to us as oil is to Saudi Arabia.

They are a prime reason we live here, and why visitors brave the high cost of air travel to come here. Let's keep our beaches clean: After all, it's in our personal, ecologic and economic interests to do so.