Most manufacturers make cargo nets that have some stretch and have built in connectors to attach to the cargo hooks. These really help with things shifting around, not totally sure how much they'd help in an accident, I'd think some.
There are also barriers that attach to the ceiling and form a barrier behind the 2nd row of seats. These are often marketed for pets, but are basically to secure things behind the seats. The OEM ones, if your manufacture makes ones, will be designed specifically for the vehicle and attach securely and safely. They often come in a netting type or a steel barrier.
My 1st and 2nd cars were hatchbacks and then my 3rd and current have had liftgates, so I've always had the open cargo area issue. Typically I use a cargo net for light items, groceries, etc. and then we use the ratcheting straps for heavy stuff. Costco usually sells a set of ratcheting straps for a decent price.