In Detroit and around the world, automakers are struggling to maintain sales in the face of new competition from mobile services like Lyft and Uber. These ride-sharing startups have spread quickly in most major American cities, connecting consumers to drivers accepting fares through the services. Then there’s startups like RelayRides, which allow people to rent vehicles for short periods of time.

All these startups have one thing in common — they make it easier to function in the United States without owning a car. That makes companies like Ford and General Motors very nervous. Now, those companies are experimenting with similar crowdsourced services to make up for losses to digital competitors.

Experts say mobile apps like Uber will only become more popular in the years to come. Increasingly, U.S. consumers access the Web through their smartphones, and mobile advertising revenue will more than triple in size by next year.

This June, Ford began testing a car-sharing program that would allow Ford buyers an easy way to rent out their cars. The Ford pilot program is modeled off yet another crowdsourcing app, Airbnb, and the automaker has called it the “Smart Mobility Plan.” The six month program will be limited to Ford customers in Berkeley, Oakland, San Francisco, Portland, Chicago, and Washington D.C.

Then there’s General Motors, which recently launched a mobile app of their own in Germany. GM’s CarUnity app allows car owners to rent their ride to friends or customers in the app network.

Thilo Koslowski, vice president at research firm Gartner Inc., says that a decade from now, at least 20% of urban cars will be shared between drivers.

“This is a big bang moment for the auto industry,” Koslowski said. “Imagine all of a sudden 20% of your vehicles sales in the classic sense — to individuals who will be the only user of that car — go away.”

The market for car ownership in developing countries will offset losses in Europe and the United States, for now. But experts say that for every one vehicle dedicated to a car sharing or short-term rental service like Lyft or ZipCar, between four and six new car sales disappear.