The state of the world's plants is not strong.

One in 5 plant species faces risk of extinction, according to a report touted to be the first assessment of global plant life. And such loss of plant diversity could have devastating impacts on our own plant uses.

"Plants are absolutely fundamental to humankind," Kathy Willis, science director at the Royal Botanic Gardens at Kew in London, who led the new report, told the Guardian. "Plants provide us with everything – food, fuel, medicines, timber and they are incredibly important for our climate regulation. Without plants we would not be here. We are facing some devastating realities if we do not take stock and re-examine our priorities and efforts."

The good news is that deforestation rates around the world have declined considerably since the 1950s, with Brazil and China demonstrating significant success. However, this first-ever report on the health of plant species around the world shows that there is much more to be done.

The report, called the "State of the World's Plants," estimates that there are currently 390,900 plant species known to science, not including algae or moss. This estimate accounts for instances where scientists have described the same species with different names. And some 21 percent of those plants are threatened with extinction, according to the report.

"The positive is we're still discovering lots of new plants, about 2,000 each year, new plants for food, for fuel, for drugs," Dr. Willis told the Associated Press. "On the negative, we've seen a huge change in land cover, mainly driven by cultural activity, with a little bit of climate change in there as well."

Human activity has a significant impact on plant extinction risk. As humans chop down forests to clear space for agriculture, and towns and cities, vast stores of biodiversity are lost.

"If we completely clear the land and have a type of monoculture what happens when a new plant disease emerges and wipes out the crop entirely?" Steve Bachman, a species conservation researcher at RBG, said to Reuters.

Deforestation for land use change is compounded by the impacts of climate change, both by affecting plants that are highly sensitive to changes and through indirect impacts, like changes in pollinators.

Plant species extinction could have reverberating effects. Plants act a bit like lungs for the Earth, sucking carbon dioxide out of the air. Plant loss means reduction in this carbon sink.

Losing the diversity of plants could also be a problem for human use, as at least 31,128 plants are currently put to some documented use. Not only could this affect our own food supply directly, it could also affect the food web. If a plant-eating animal loses some of its food source, that change could be felt up the food chain.

"I am reasonably optimistic," Willis told The Guardian. "Once you know [about a problem], you can do something about it. The biggest problem is not knowing."

Identifying new species and keeping a catalogue of plant types worldwide is a step toward protecting global plant diversity, the researchers say.

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"If this plant doesn't have a name, and it falls over in the forest, no one knows," Timothy M.A. Utteridge, head of identification and naming at the Royal Botanical Gardens, told the Associated Press. "Once we have a specimen, and a name, we put that on the map."

This report contains material from the Associated Press and Reuters.