New report highlights loss of valuable soil in urban areas

A new report says we aren't doing enough to protect our soil in urban areas, resulting in a precious resource being wasted.

Healthy soil in urban areas plays a crucial role in draining stormwater to prevent flooding, and providing root space for trees to grow in increasingly hot cities.

But a new report by the Parliamentary Commissioner for the Environment says its value isn't recognised and it is often stripped from building sites and dumped, or paved over.

The findings are relevant to Auckland's need to adapt its urban planning and design as more intense rain events occur, resulting in extreme flooding. 

Climate change means we'll also see extremes on the other end of the spectrum, and healthy soil will be increasingly valuable as a buffer to heavy rainfall and to help trees and plants flourish, Parliamentary Commissioner for the Environment Simon Upton said.

"We haven't yet had a really, really serious heatwave, but when we do - and that's coming - that is going to suddenly focus people on how hot our suburbs are."

Manaaki Whenua researcher Jo Cavanagh said healthy soil is hugely undervalued.

"Fundamentally it comes down to not recognising the value of soil and in particular the beneficial properties it has," Cavanagh said.

Those properties include providing root space for trees to provide shade, and slowing down stormwater.

The latest report from the Parliamentary Commissioner for the Environment, called 'Urban Ground Truths', highlights a lack of protection in council plans for high-quality soil amid increasing demand for urban development.

Cavanagh said there is a lack of recognition and a lack of consistency in how soil is defined in council plans.

The report notes that the way we build usually means removing topsoil and subsoil rather than preserving it.

"If you do that across the entire space because it's cheaper and quicker, even where you're not building a house you remove the soil, you're left with nothing," Upton said.

Upton said regulations and building standards need to be aligned to preserve as much good soil as possible.

He recommended national guidance be issued to provide clarity and consistency on the depth of landscaped soils for grass, green areas and shade-bearing trees within urban developments.

"We don't have to make a meal of everything, we don't have to make everything a high political priority which dances in neon lights.

"This is bread and butter stuff, if we can do it better, let's do it better."