Mr James works on the Heathland Nature Reserve around Woodhall Spa and said adders were "in desperate need of help".
He said the reptiles hibernate from October and emerge in spring.
During this time, they bask in sunlight, shed their skin, build up their body temperature and can often be seen.
This process is the adder's "critical period", according to Mr James and, if they are disturbed, they will not eat because of stress.
"They're surviving on the previous year's fat reserves," he said.
"They're slowly starving to death."
'Keep them chilled'
Adders, according to Mr James, "suffer an enormous amount of stress".
He said, no matter how tempting it can be to get closer to one, people should refrain, give the snake "a wide berth" and leave it alone.
"They need peace and quiet," Mr James said.
"Look then leave. Keep them chilled."
Adders can be found in England, Scotland and Wales, but not in Northern Ireland.
They are distributed across much of Europe and Asia and within the Arctic Circle.
Research from the University of Reading in 2019 said adders could "all but disappear from the UK countryside by 2032".
Lincolnshire on BBC Sounds latest episode of Look North here.
