It might come as a shock to anyone who loves pandas, but these lumbering black and white creatures are not the most practical for the ecosystem. Nothing and nobody eats them, they barely interact with other species and have a hard time reproducing. On a more positive note, they help spread the seeds of the bamboo they spend many hours a day chewing, and have become a public face for conservation.

Another beloved bundle of fluff that falls into the same category has to be the koala. Australia's iconic marsupials spend more than 80 percent of their lives asleep, and the rest of the time eating eucalyptus. Like giant pandas, they don't feed on any other creatures and none seem to have acquired a taste for them. They don't even spread eucalyptus seeds. But they are pretty cute.

This fly might be welcome at the wasp's dinner of strawberry jam, but as a species they're not universally loved. On the contrary. We dislike their buzz, tasteless passion for feces, and ability to spread disease. That said, they can actually be useful. Apart from being spider food, some of the more than 110,000 fly species pollinate flowering plants.

Imagine a beautiful summer sunset — and now the swarm of mosquitoes ready to suck your blood. As with flies, we would all be happier living in a mosquito-free world, especially since they can transmit deadly diseases. But mosquitoes are a main source of food for birds, fish and mammals. And even if we did wipe out most of the mosquitoes, scientists believe new breeds would soon replace them.

We might like to think of wasps as the useless, often aggressive cousins of bees. But that's not the real story. Wasps are great pest fighters, preying on insects and parasites that wreak havoc on crops — sometimes by being particularly nasty and laying their eggs inside them, as they do with some caterpillars. They also pollinate plants and flowers as they feed on nectar.

OK, what about ticks and fleas? Apart from sucking blood, they're totally useless, right? In fact, some species of reptiles and birds feed on the insects, thereby benefiting from the blood they've sucked up from larger animals. And because they spread diseases, they help control wild animal populations. Their role might not sound pretty, but they do seem to have a purpose in life.

It's clear that most, if not all species on this planet have earned their place — even the annoying ones. But there's one species we're forgetting, and that's ourselves. If there were a prize for Earth's most useless species, humans should definitely be in the running. After all, there's one thing no other species does better than us: devastate nature.