Red tape is making it "far easier" to cut woodlands down in Wales than to create new ones, a charity has warned.
Chris Matts, from the Woodland Trust, said "nature-based systems" are some of the most important tools for tackling climate change, but said bureaucracy was an issue.
Government statistics show the number of trees being planted is increasing, but conservationists have said it is not keeping up with targets.
The Energy and Climate Intelligence Unit predicts that, based on current planning rates, Wales will only meet 10% of its target by 2030, "lagging behind" other devolved nations.
The Welsh government said the statistics do not take into account everything happening on Welsh land.
Keith Roberts, a volunteer with the Woodland Trust who helps maintain a woodland area in Neath, said he gets "a strong sense of ownership" from the area.
"One of the main reasons for planting the trees is part of the local flood defence system, so that's why we wanted to get involved in making the whole area safer for the Neath residents."
"The whole point is creating something for future generations," he said.
Trees can help tackle climate change by absorbing carbon dioxide, offering cooler shaded areas in hot weather and acting as part of flood defence systems.
The Climate Change Committee (CCC), an independent body advising UK nations, includes woodland cover as part of its recommendations for reaching emissions targets, as well as preparing for and adapting to the impacts of climate change.
Devolved governments use the committee's recommendations to set their own targets and plans.
That view is echoed by the Energy and Climate Intelligence Unit, a climate not-for-profit think tank, which says its analysis shows that, compared to CCC advice, by 2030 the UK is set to have a tree planting gap of more than 4,000 hectares - an area equivalent in size to the city of Portsmouth.
Tom Cantillon, a senior analyst with the group, said that based on current tree planting rates, Wales is set to achieve about 10% of its government Carbon Budget 2 target and 27% of CCC advised levels by 2030.
Scotland is set to achieve 74% of its own government target and 98% of CCC advice by 2030, while Northern Ireland is on course to achieve 48% of both its own government target and CCC advice over the same period.
"Underplanting now will have significant knock-on impacts on the UK's net zero ambitions – due to the time lag between when a tree is planted, and when it can effectively remove carbon from the atmosphere," Cantillon said.
"It does raise questions for the Welsh government in how that shortfall in tree planting will be made up for in the future, either with more planting or with other actions across the wider economy."
The Confederation of Forest Industries (Confer), a membership organisation which lobbies on behalf of the private forestry and wood sector, said the data shows we are "failing future generations".
Elaine Heckley, the organisation's Wales manager, said: "This is a dismal failure, when all the evidence shows that we need to plant many more trees to create green jobs, build sustainable homes and support our climate change ambitions."
In response, the Welsh government said the statistics only reflect areas meeting certain criteria and do not take into account every tree planted on Welsh land.
"Increasing tree cover benefits our environment and the health of people in Wales, and will be felt for generations to come," a spokesperson said, adding that it was "committed to increasing tree planting rates".
"We will be working collaboratively with public sector bodies to better understand the contribution they can make to increasing canopy cover in Wales," they added.
