Editor's note: Matt Rand directs the Pew Environment Group's Global Shark Conservation Campaign and is an avid fisherman and certified diver.

(CNN) -- Few members of the animal kingdom have grabbed our imagination as much as sharks. From 1975's summer blockbuster "Jaws," to 2004's animated film "Shark Tale," these marvels of the deep have been a staple in U.S. pop culture -- a trend that continues as viewers this week watch the Discovery Channel's latest edition of "Shark Week."

Yet even though they have earned a reputation as fierce predators, in reality it is sharks that are the hunted. Unless we act soon, re-runs on cable TV may be among the few places sharks can be seen.

For hundreds of millions of years, sharks have ruled the oceans. Predating dinosaurs, these natural wonders have adapted over the ages to survive the harsh climatic changes that doomed many other species to extinction. Sharks often serve as a keystone species by culling the sick and diseased to maintain balance in the marine ecosystem.

But their reign at the top of the marine food chain is threatened. Sharks are speedy and powerful hunters, but they also grow very slowly. Unlike other fish, sharks don't lay large numbers of eggs, but instead give birth to small numbers of live young.

They typically mature late and produce relatively few offspring, making them particularly vulnerable to modern industrial fishing practices. Many species of sharks -- from the great white to the iconic hammerhead -- are in danger of being fished to commercial extinction. A major culprit is soup.

At one time, shark fin soup was considered a delicacy for the elite. But as Asia grows in population and wealth, the demand for shark fins has gone through the roof. According to the United Nations, shark fin imports to Hong Kong and Taiwan alone rose 214 percent from 1985 to 1998. This has had a disastrous impact on shark populations globally.

The wasteful practice of "finning"-- slicing off a shark's fins and discarding the animal to die at sea -- is one of the biggest threats to populations. Indeed, up to 73 million sharks are killed annually across the globe to support the shark fin trade.

The U.N. estimates that more than half of highly migratory sharks are either overexploited or depleted. In the United States, populations of some shark species, such as dusky sharks, have declined by roughly 80 percent since the 1970s. Dusky sharks are so depleted that scientists at the National Marine Fisheries Service estimate it could take from 100 to 400 years to rebuild their populations, even with strict fishing limits. These mighty creatures, however, don't have that long to wait.

Over the past year, leaders from around the world have stepped up in defense of sharks. In 2009, the small Pacific island nation of Palau created the first national shark sanctuary -- declaring protections from all commercial fishing in an area of water about the size of Texas.

Closer to home, the U.S. House of Representatives unanimously passed a bill in 2009 to help close legal loopholes in U.S. law on shark finning. A companion measure is pending in the U.S. Senate. These efforts should be applauded, but if we are to truly save sharks, we need action on a much larger, more global scale.

In this U.N.-declared International Year of Biodiversity, world leaders will come together to talk about preserving species, as the U.N. prepares for its fall session. They -- including President Obama -- should call for concrete and meaningful action to conserve sharks globally, ensuring their survival. This includes restrictions on both the number of sharks that can be caught and on international trade in shark products, as well as the establishment of additional marine reserves where sharks are free from overexploitation.

While new video technology can provide us with an amazing glimpse into the lives of these age-old masters of the deep, as demonstrated during "Shark Week" and other popular shows, it's hard for any documentary to truly capture the full scope of the threat that shark populations face around the globe.

We can't sit by while a species that survived the extinction of the dinosaurs is being pushed into oblivion by the demand for an exotic bowl of soup.

The opinions expressed in this commentary are solely those of Matt Rand.