Superiority of native worms over introduced unearthed

Native species did not adapt to the conversion from native vegetation cover to agricultural pastures in New Zealand, while exotic species were able to.

Evidence suggests the worms may need to turn.

The article Agroecology niche for New Zealand's native earthworms, co-authored by Lincoln University’s Professor Nick Dickinson, states the soil fertility of agricultural lands may be influenced more by native species than exotic species.

Canterbury alone has 25 recognised species of native earthworms, but native earthworms are almost entirely absent from New Zealand's agricultural pastures.

They are now almost entirely restricted to small fragments of native vegetation on marginal land, where they coexist with the newcomer exotic European earthworms.

Their introduction to the pastures would benefit the land, the primary sector and the worms themselves.

“Future co-existence of communities of native and exotic earthworms in agricultural pastures appears realistic, and this would benefit conservation of native species as well as dairy production,” the paper stated.

The deep burrowing native worms made more nitrogen available to plants than the exotic and increased mineralisation, or the decomposition of organic matters by microorganisms to release inorganic compounds that can be readily used by plants to help their growth.

Professor Dickinson said deficiencies of various nutrients such as copper and zinc for plants and animals are widespread in New Zealand soil.

“Given this fact, the marked enhancements of bio-availability of some minerals by burrowing or casting of two native species would suggest that the presence of native earthworms have the potential to further improve the fertility of New Zealand pastoral soil.”

However the article highlighted that more work needed to be done to unearth the benefits of the native worms.

“Further research may also reveal additional and unique benefits to soil quality that could be attributable to this formerly unavailable niche for native earthworms.”