There were no prosecutions for environmental pollution in Northland courts last financial year.
Ministry of Justice figures show five years earlier, during the 2010 to 2011 financial year, there were 79.
A Ministry for the Environment spokesperson said enforcement of the Resource Management Act was the responsibility of local authorities.
Prosecution was only one of a number of formal enforcement options and normally a last resort. Other options included abatement notices and enforcement orders, letters and verbal warnings.
Whangarei environmentalist Peter Coates said he was surprised the level of prosecutions had dropped.
He thought both the city and regional council were aware of environmental problems and acting on them.
"I certainly haven't noticed any lessening of interest on the part of councils... in fact quite the opposite, I think that the councils are becoming more aware."
He said it was better for councils to get onside with those causing environmental damage than work against them, however that could take time.
"Change does take time and we have to be prepared to accept that and pay for it."
In his experience, people in Northland were becoming increasingly aware of pollution and trying to act on it.
Nationally, the number of environmental pollution prosecutions has more than halved over the past five years. There were 555 prosecutions in the 2010/2011 financial year and 234 last financial year. Last year, 38 per cent of cases resulted in convictions compared to 43 per cent in the 2010/2011 financial year.
University of Auckland Associate Professor Kenneth Palmer said he was not surprised the number of prosecutions had dropped.
Dr Palmer's teaching and research interests include environmental law, resource management law, and local government law. He thought people were becoming better educated about environmental responsibilities.
Farmers had proper effluent treatment measures, regional councils were making sure farms were complying with the rules and people weren't polluting the way they used to. Enforcement around the transportation of hazardous substances was also stricter.
"So overall, better standards, better education, safer practices. So that's good news that people are getting the message and are now not trying to get away with things."
Dr Palmer said he did not have concerns over the rate of conviction as identifying offenders could be an issue in pollution cases.
There were also defences if somebody did cause pollution and there was nothing to stop somebody receiving a summons going to council and trying to work out a compromise. Dr Palmer said in many areas where there had been no prosecutions it was likely the level of enforcement was good, breaches were not particularly serious and nothing justified the substantial cost of a prosecution and delay in getting a hearing.