South Holland has lower tree coverage across its parks, woodland and streets than anywhere else in England, new figures show.
Analysis conducted on behalf of Friends of the Earth by mapping experts Terra Sulis has identified lone and street trees, which were not previously captured.
It shows just 2.2% of South Holland is covered by trees, the lowest percentage in the country.
In England, tree canopy cover stands at just 12.8%, of which only 10% can be attributed to woodland. Across the European Union, woodland cover rises to 38%.
The Government's current goal is to increase tree coverage to 16.5% by 2050, but climate charity Friends of the Earth said this is "inadequately low", and argued double the current figure would be more reasonable.
Meanwhile, 43% of neighbourhoods in England have less than 10% tree cover, while 84% have less than 20% coverage.
There are also huge regional differences – while South Holland has the least tree coverage, Surrey Heath has the most with 36.1%.
March 21 is the United Nations' International Day of Forests. The theme this year is "Forests and Health", raising awareness of the health benefits higher tree coverage can have on the local population.
Mike Childs, head of science, policy and research at Friends of the Earth, said: "The Government should be aiming to double tree cover in England by 2050 to ensure that people, no matter where they live or what their income, can experience the mental and physical health benefits that trees bring.
"Current targets for tree planting are woefully inadequate and overlook the devastating impact that timber and wood imports from countries such as Brazil, China and Russia wreak on nature globally.
"We need many more trees for farming, urban cooling and absorbing harmful carbon emissions. The Government must get behind a far more ambitious plan to boost tree numbers and adopt this as an official target."
Tree coverage roughly tracks levels of deprivation across the country, with the most deprived areas generally having fewer trees.
Census figures from the Office for National Statistics show 44% of 40,703 households in South Holland are not deprived in four key areas – housing, education, health and employment.
It means the area follows the national trend, as it ranks 308th for tree coverage and is the 257th least-deprived.
The Department for Environment Food and Rural Affairs said the Government is committed to trebling average tree planting rates, boosting the number of trees close to where people live and in nature-deprived parts of the country.
It said £650 million of funding is focused on the "planting and establishment of trees in urban areas".
A spokesperson said: "Increasing tree and canopy cover across England is part of our plan to tackle the impacts of climate change and the biodiversity crisis."