Malcolm Roberts promised, and Malcolm Roberts delivered. After announcing on Facebook that he would address the threat to Australian sovereignty from “Agenda 21”, he raised it in his first speech as an Australian senator. After extended remarks intended to refute the scientific consensus on climate change, and a comparison of himself to Socrates, Roberts said that:

people are waking to the UN destroying our national sovereignty through implementation of the UN’s 1975 Lima declaration and 1992 Rio declaration for 21st century global governance, often known as Agenda 21 – more recently as Agenda 2030.

Roberts said that following the then-Keating government signing the Rio Declaration in 1992, it has been “sneakily implemented by ministers of every government since under the guise of biodiversity to steal property rights, sustainability to pass regulations controlling people and climate change to push foreign control using unlawful agreements like the Paris sham”.

For these and other reasons, Roberts wants Australia to leave the UN.

What is he talking about? In reality, the Rio Declaration is an entirely nonbinding and voluntary agreement which 178 countries entered into at the Rio Earth Summit almost a quarter of a century ago.

Its aim was to promote a vision of sustainable development by combatting poverty, disease and overpopulation; fostering conservation, atmospheric protection, pollution controls and biodiversity; and by establishing a greater role in all of this for non-state actors like women’s groups, young people, NGOs and business.

It also promoted local participation – many cities and local authorities around the world have signed up to ICLEI – also known as Local Governments for Sustainability – which encourages their participation in implementing Agenda 21 initiatives.

It’s not a treaty, does not override national sovereignty and does not allow the UN to dictate what governments do. It has no legal force and is not intended to be implemented in a top-down way.

Nevertheless, almost as soon as it was inked, Agenda 21 became the focus of conspiracy thinking, which at first mostly came from the far right.

The main thrust of most of those conspiracy theories echoes Roberts’s remarks to the Senate: Agenda 21 is in fact a UN plan to deprive nations of their sovereignty, and individuals of their property rights.

On the fringes of the right, a benign agreement encouraging social and environmental stewardship became a disguised attempt to impose global communism on free citizens.

Tom DeWeese, an American rightwing activist who heads up the American Policy Center, was one of the earliest critics of the agreement, and has remained consistent in his claim that sustainable development is a “utopian, socialist nightmare”.

Like Roberts, DeWeese wants his country to pull out of the UN, and also cites the erosion of national sovereignty and property rights as the main dangers posed by Agenda 21, which is voluminously attacked on his website.

The John Birch Society – infamous for its decades-long crusade against imagined communist conspiracies – also played a key early role in pushing the idea that Agenda 21 was communism in another guise.

During the late 1990s, the burgeoning militia movement in the US took the view that Agenda 21 was part of a grand plan to institute one world government – the plan for sustainable development was the first step on a road that would lead to the UN’s black helicopters landing on the White House lawn to dismantle the Republic.

This belief has persisted on the armed, radical right – the Bundy occupation of the Malheur Wildlife Refuge last January was driven in part by the idea that local ranchers were being deprived of grazing rights under the aegis of Agenda 21.

In recent years, though, paranoia about Agenda 21 has become mainstream via rightwing media stars and politicians. Probably the most important advocate has been Glenn Beck, who has spruiked the conspiracy theory on television and radio.

He even authored a dystopian science fiction novel which envisaged an America under the yoke of global, environmentalist government.

The blurb provides a neat summary of the fear at the heart of anti-Agenda 21 activism:

Just a generation ago, this place was called America. Now, after the worldwide implementation of a UN-led program called Agenda 21, it’s simply known as “the Republic.” There is no president. No Congress. No Supreme Court. No freedom.

As usual, the real danger in far right beliefs is the way in which they cross over into mainstream conservative politics.

Mainstream political figures in the US – among them former presidential candidates Ted Cruz and Newt Gingrich – have warned in dark terms about the danger posed by Agenda 21.

As the theory caught on among the Republican grassroots in the last decade, several US state houses passed resolutions condemning it, and Alabama even passed a law specifically aimed at its imagined danger to property rights.

And in Australia, Nick Minchin, a former Howard government minister and mentor to current rightwing powerbroker Cory Bernardi, voiced similar sentiments to the anti-Agenda 21 movement without naming the agreement.

On efforts to combat climate change, Minchin told the ABC’s Four Corners in 2009 that:

For the extreme left, it provides the opportunity to do what they have always wanted to do, which is to sort of de-industrialise the western world. The collapse of communism was a disaster for the left and, really, they embraced environment as their new religion.

Malcolm Roberts couldn’t have said it better.

In general, the debate about climate change in Australia has been poisoned by a belief – shared by the far right and some mainstream conservatives – that climate science is basically a leftist plot. Roberts continues this tradition.

Some will dismiss him as a harmless kook, and point out that One Nation are nowhere near the levers of power. But in a finely balanced Senate, in which Roberts’ beliefs are effectively shared with some members of the Liberal party, it’s not a stretch to think that Roberts will be able to act to prolong delays in this country coming up with an effective response to climate change.

The danger of the far right, as always, is in their relationships with ostensibly mainstream actors, and the way in which their conspiracy thinking affects policy.