Airport dogs are great, they work like ultra sensitive living walking xray machines. They detect and prevent the transport of all sorts of illegal and dangerous items including the trafficking of live, wild animals, and their body parts (for example horns). This also carries over to how the dogs prevent the invasion of plant and animal species. If an animal is brought into a new ecosystem, it might not have a natural predator and will reproduce like mad. This then results in the native animals being hunted by them till extinction.
The dogs are also trained to sniff out cash. But don't worry, it's only a problem if you are bringing over 10k in cash undeclared.
Some airport dogs are even capable of smelling ailments like cancer and Parkinson's Disease. In the UK for example, the airport dogs are trained to detect malaria to not only prevent the spread but also eradicate it. With an over 70% success rate, the dogs are a great help.
Sometimes you might even see an airport dog providing comfort to stressed out passengers. Not everyone has flown in a plane before and some people have heard of way too many plane crashes. No matter the reason, the dogs are there to lend a helping paw.
But most importantly, they prevent bombs from taking off. This is probably the only thing on this list that actually saves human lives.