(CNN) International targets to cut emissions and limit climate change will be missed due to rises in deforestation and delays in changing how humans use land, a new study warns.

Nearly 100 countries pledged to make their use of land less damaging to the climate, mainly by limiting deforestation rates and boosting forest restocking, when they signed the Paris Agreement in 2015

But those commitments were unrealistic and need to be stepped up dramatically, according to researchers at the Karlsruhe Institute of Technology and the University of Edinburgh, who pointed to inaction by richer countries and a rise in deforestation in several countries since the treaty was signed.

The agreement committed almost 200 countries to keep global warming well below 2 degrees Celsius above pre-industrial levels -- and below 1.5 degrees if possible.

"In most cases, little progress has been made, [and] often, the situation has actually worsened in the last three years," said Calum Brown, lead author of the study, published Monday in the journal Nature Climate Change.

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