David Parker is like water on stone.
A conviction politician who never gives up on cherished ambitions, his hand can be seen in the last two decades of policy action on some of the country's knottiest challenges: climate change, electricity, freshwater, the Resource Management Act, even foreign investment.
A minister in the Helen Clark-led government of 1999-2007, he shepherded the emissions trading scheme into existence, then saw it achieve very little in nine years of National-led government.
Re-elected to a government in 2017, he's been donkey deep in reviving it.
He was also an early mover on freshwater policy reform, although that did see progress under National.
The Land and Water Forum, a brainchild of National's first Environment Minister, Nick Smith, created a ground-breaking platform for various traditional opponents to work collaboratively.
Maori, farmers, environmentalists, recreational users, and local government representatives laboured to find what common ground they could in an area of fiendish complexity.
It was a slow grind, particularly compared to the stampede into dairy farm conversions unleashed, in large part, by the China-New Zealand free trade agreement signed by the Clark government.
As Trade Minister today, Parker seeks to promote a new era of trade deals that acknowledge the wave of scepticism that is sweeping global politics about the benefits of globalisation while preserving the market access that New Zealand agricultural exporters need.
Yet even as he does that, as Environment Minister, Parker is embarking on proposals to accelerate the clean-up of New Zealand's increasingly polluted freshwater lakes, rivers and streams in ways that will surely change forever the mix and quantity of agricultural exports that this country produces.
That is the underlying implication of the "Action for Healthy Waterways" discussion document that Parker released last week.
A growing chorus of farm sector lobbyists is warning the proposals are likely to force some farmers off some land.
Not only are they right about that – or at least that they will have to farm something different in future – but if that is not the outcome, then policy won't have worked.
Hand in hand with the hugely ambitious targets for methane emissions reduction under the Zero Carbon Bill, the freshwater proposals seek to "hold the line" and start swiftly reducing nitrate, phosphorous and sediment run-off from farming.
As the document itself says: "good farming practice can achieve some but not all of the reduction in nutrient pollution required to achieve ecosystem health.
"Reaching the proposed new bottom lines across the country would mean tighter restrictions on nutrient run-off in low lowland agriculturally-dominated areas, beyond existing limits, especially in parts of Waikato, Canterbury and Southland."
To ram home the urgency, Parker is proposing a fast-track process for regional councils to update their freshwater management plans by 2025, following advice from many councils that they would need until 2030 to put new plans in place.
That was too slow for Parker, who appears determined that this is one of area of government policy where there will be minimal backsliding. For Labour and the Greens, cleaning up rivers was an election promise in 2017.
So, capital gains tax may have been a bridge too far, and KiwiBuild a dream too large, but Parker is righteous in his pursuit of cleaner waterways, not just for the environment, but also because New Zealand's reputation as a clean food producer will ultimately suffer if the water used to produce that food is not clean.
The cost, roughly estimated by officials in the documents, looks like the thick end of at least $1 billion over 10 years, which looks like a lot but needs perspective.
At $100 million a year, these costs represent less than 1 per cent of the roughly $12b of raw agricultural output that StatsNZ measures annually.
On its own, that cost should be manageable.
However, it comes at a time when farmers feel under assault from both a tsunami of government-induced policy change across the change policy, water, bio-security, food safety, health and safety, and other fronts. In the case of Fonterra shareholders, there is the added worry of whether their cooperative will or should survive in its current form.
The extent of Fonterra's concern for appropriate political positioning was most evidence in its proactive release of a statement welcoming the government's freshwater policy proposals at the same time as the more apoplectic end of Federated Famers claimed farmers were being "thrown under the tractor".
Their president, Katie Milne, struck a more conciliatory tone in interviews, but as Iain White, a professor of environmental planning at Waikato University told the Science Media Centre: "while a focus on shared responsibility reflects the reality of the situation, it also links to the practical political difficulties in aligning decision-making around a shared vision when this is such an intensely political issue".
As difficult as a workable, auditable regulatory and compliance regime will be to establish for new freshwater standards, it may be easier to achieve than widespread farmer buy-in.
Achieving a 'hearts and minds' willingness in enough of the farming community to actually tackle these challenges is itself a hugely challenging task.