AgResearch scientists have been doing a survey on earthworms to find out where they are distributed to help improve agricultural production across the country.
The last time a survey of this type was conducted was in the 1980s. It showed some types of earthworms were not present in parts of New Zealand, while other regions were lacking worms altogether. All the earthworms in the country's pasture systems are exotic.
A post-doctoral researcher at AgResearch, Nicole Schon, said scientists were having another look to see what had changed since the 1980s survey.
"(We're) getting a better understanding of the current distribution of the earthworms. In particular we're interested in the deep burrowing earthworm.
"This is one that we've found is often absent from our pastures, so if we can find out where they're absent, we can introduce them to those pastures to benefit production.
She said earthworms did two main things.
"They eat the organic matter and incorporate this into the soil and stimulate nutrient cycling.
"The second thing that they do is burrow through the soil, so they promote soil structure and aeration and help water movement through the soil. Both of these factors help to increase pasture productivity."