It’s going to be a big day tomorrow when the Oregon football team comes to town.  This year, we meet the team that handed us our only loss last season – but on our own turf.  And although Stanford has played (mostly) with convincing dominance this season (and Oregon’s already picked up one loss), we’ll take all the home-field advantage we can get.

Sports fans everywhere understand the merits of playing at home: you know the quirks of the stadium, are acclimated to the local weather, and have a fan base that screams at your opponent and shuts up when you’re on offense.  It’s the classic recipe for success.

But if you’re the rare team that plays best on the road, you might just shake up the league.

That’s what happens in nature, when some species – transported far from home by human activity – launch ecosystem-rattling invasions of local plant and animal communities.  Invasive species can change landscapes, clog waterways, squeeze out locals, and even poison wildlife.  And unlike a visiting sports team, which catches an outbound bus after even the most disheartening trouncing, invasive species come to stay.

What makes these alien invaders so successful?  First, they have to travel well, and carve out a foothold wherever they land.  Once established, they might be faster-growing than their local equivalents.  Or their usual predators might be absent in the new environment.  The factors differ for every species – and in each locale – making invasions hard to predict.

One thing we do know for sure, though: Invasive species are a growing, global problem.

Every year, the United States alone spends about $9 billion trying to control aquatic invaders (to say nothing of kudzu, iceplant, Eucalyptus, and other terrestrial troublemakers).  San Francisco Bay alone hosts more than 250 nonnative species, making it one of the most invaded spots on the planet.

In fact, the first report of marine invaders on the West Coast was logged in the bay – in 1853, someone stumbled upon an Atlantic barnacle looking happy as a clam.  Since then, swimmers itch, Asian crabs, and a host of other species have arrived.  On average, a new species arrives about once every 14 weeks.  Prior to 1961, the invasion rate was only about one species per year.

Why here?

Global commerce is a major factor.  In 2008, Jennifer Molnar and colleagues at The Nature Conservancy published a key study on aquatic invaders, finding that cargo volume was the best predictor of invasion.  Nearly 70% of the species in their study could hitchhike on some kind of shipping vessel.

There are a number of ways for aquatic organisms – which usually travel during their tiny, free-swimming larval stages – to hitchhike.  They can tuck themselves in and among barnacles and algae growing on the ship’s hull, or they can hang out in the ship’s ballast tanks, onboard chambers pumped full of water to add mass to a ship in heavy seas.  Commercial ships travel long distances – and fast.  Most coastal marine creatures can only drift for a few weeks before they need to find a piece of real estate to settle down.  That’s generally not enough time to drift across an ocean basin.  But get sucked into a ballast tank in Shanghai on a Monday, and you could get pumped out in Oakland by Friday of next week.

Ports, then, become the gateway for invaders – and the place we look to stop them.  Most strategies call for better management of ballast water – particularly, reducing the amount of live organisms that get pumped out of tanks while ships are in port.  Commercial vessels are now supposed to flush out their ballast tanks mid-voyage, hoping to evict any coastal critters where they have no hope of making landfall.  But while this is somewhat effective with freshwater species (which generally don’t tolerate saltwater), marine larvae often persist in nooks and crannies.

Under pressure from conservation organizations, the United States Environmental Protection Agency is expected to release new guidelines for the Vessel General Permit (required for all commercial operations) by the end of this month.  These guidelines will toughen limits on the “living pollution” that ships discharge when they flush tanks in our coastal waters.  These guidelines come with costs: equipping a fleet with filtration systems, chlorine treatments, or UV lights may kill off potential invaders, but it could also kill off business.

That’s why people perk up when they hear University of Michigan Professor Michael Parsons talk about the “ballast-free ship”.  Instead of static ballast tanks, his design uses a flow-through pipe system of adjustable capacity.  As the ship moves forward, the surrounding water flows through the system, continually flushing out eggs, larvae, and the odd jellyfish that might’ve tried to tag along.  According to Parsons, who spoke last week at Hopkins Marine Station in Monterey, such ships would be cheaper to operate than vessels retrofitted with other invasion-control measures, but they would need to be built from scratch.

Though the ballast-free concept was patented in 2004, it will probably take a firm kick from the EPA before we see fleets cruising under the Golden Gate.  That is, if Republican-led legislative efforts don’t undermine the regulations first.  Meanwhile, California is preparing to implement restrictions that are 1000-times more stringent by January 2012.  Because here, we know how to root, root, root for the home team.