Scientists aren't sure how many millions of species there are in the world, but they know for certain that humans have driven some of them to extinction, wiping out creatures such as the dodo, the Tasmanian tiger and the passenger pigeon.

A a new study indicates that the number of species lost each year is even higher than earlier thought, with researchers estimating that between 100 and 1,000 species disappear yearly, Live Science reported.

Published Thursday in the journal Science, the findings are sobering but still optimistic since technological advances and citizen scientists have both served to boost conservation efforts, according to study researcher Stuart Pimm, a Duke University biologist.

"Although things are bad, and this paper shows that they're actually worse than we thought they were, we are in a much better position to do something about that," Pimm told Live Science.

Researchers believe that the typical extinction rate for Earth's species before humans are thought to have appeared was around one extinction for each 10 million a year.

While species are disappearing at a faster rate, the researchers say they have renewed hope as technology helps them pinpoint endangered species and their habitats. Tools such as satellite imagery and global tracking of deforestation as well as websites and apps can all be used by scientists to watch for threats to various species.

"It's probably less than 10 percent [of land area] that has most of the species we're really at risk of losing," study researcher Clinton Jenkins, a conservation researcher at the Instituto de Pesquisas Ecológicas (IPÊ) in Nazaré Paulista, Brazil, told Live Science. "So if we focus on those areas, it can solve most of the problem."

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