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Good morning, I’m Tim Walker with today’s essential stories.

Mnuchin says tax demand ‘lacks a legitimate legislative purpose’

The Trump administration’s bitter fight with its political opponents ramped up on Monday, as the Treasury department flatly refused to release the president’s tax returns, while House Democrats set up a vote to hold his attorney general, William Barr, in contempt of Congress. The Treasury secretary, Steve Mnuchin, wrote to the House ways and means committee chairman, Richard Neal, that the “unprecedented” request to see Trump’s tax returns “lacks a legitimate legislative purpose”.

Letitia James. The president’s tax returns could emerge another way, if they are subpoenaed by the new attorney general of New York, Letitia James, who has called Trump “an illegitimate president” and launched several investigations of his finances and his allies since taking office.

Obstruction charges. Hundreds of former federal prosecutors have signed an open letter saying Trump would face obstruction charges based on the evidence in the Mueller report, were he not the president.

China’s destruction of mosques in Xinjiang revealed

Facebook Twitter Pinterest Satellite imagery shows the Imam Asim shrine in southern Xinjiang has been destroyed. Photograph: Planet Labs

More than two dozen Islamic religious sites in Xinjiang, the home of China’s persecuted Uighur Muslims, have been partially or completely destroyed since 2016, an investigation by the Guardian and Bellingcat has revealed. Satellite imagery suggests 31 mosques and two major shrines suffered serious structural damage between 2016 and 2018, amid Beijing’s chilling mass surveillance campaign against its Muslim minority. Of those, both shrines and 15 of the mosques appear to have been totally or almost totally razed.

Re-education camps. Researchers say as many as 1.5 million Uighurs and other Muslims have been involuntarily sent to internment or re-education camps by the Chinese government, though Beijing denies those claims.

US warns of ‘new South China Sea’ – in the Arctic

Facebook Twitter Pinterest Pompeo (right) with the Russian foreign minister, Sergei Lavrov, at the Arctic Council meeting in Finland. Photograph: Anton Novoderezhkin/Tass

The US secretary of state, Mike Pompeo, has warned that the US intends to increase its presence in the Arctic to keep in check the “aggressive behaviour” of Russia and China, threatening a fraught future for the resource-rich and environmentally sensitive region. Speaking at a meeting of the Arctic Council in Finland, Pompeo said: “Just because the Arctic is a place of wilderness does not mean it should become a place of lawlessness.”

Frozen out. China is a mere observer on the Arctic Council, not a member. Its most northerly point is 900 miles from the Arctic Circle. “There are only Arctic states and non-Arctic states,” Pompeo said. “No third category exists, and claiming otherwise entitles China to exactly nothing.”

Insect diversity warning follows damning UN nature report

Facebook Twitter Pinterest A Patagonian bumblebee – 10% of the 5.5 million species of insect thought to exist are threatened with extinction. Photograph: Michael Grant Wildlife/Alamy

A leading entomologist has warned that in order to save itself, humanity must save the insects from an impending cascade of extinctions. According to a major UN report published on Monday, 10% of the 5.5 million species of insect thought to exist are in danger of dying out. “Insects are the glue in nature and there is no doubt that both the [numbers] and diversity of insects are declining,” said Prof Anne Sverdrup-Thygeson, of the Norwegian University of Life Sciences. “At some stage the whole fabric unravels.”

Global crisis. The UN’s global assessment report, the most thorough planetary health check ever undertaken, found the biomass of wild mammals had fallen by 82%, natural ecosystems had lost about half their area, and a million species were at risk of extinction, all largely as a result of human actions.

Crib sheet

Myanmar has pardoned and freed two Reuters journalists who were arrested in December 2017 for their reporting on the ethnic cleansing of Rohingya Muslims.

Turkish authorities have scrapped the results of the Istanbul mayoral election and announced a fresh vote on 23 June, after the candidate backed by the Turkish president, Recep Tayyip Erdoğan , lost narrowly to his opposition rival.

Meghan, Duchess of Sussex, has given birth to a royal baby boy, who will be seventh in line to the British throne. Prince Harry, the child’s father, said he and Meghan were still thinking about names.

Lady Gaga wore four separate outfits and Billy Porter arrived on a litter carried by six shirtless men as celebrities walked the red carpet at the 71st annual Met Ball on Monday. The theme for 2019 was “Camp”, after a 1964 essay by Susan Sontag.

Must-reads

Facebook Twitter Pinterest A cattle stockyard in Texas in the 1960s. Photograph: ClassicStock/Alamy

How the beef industry created modern agriculture

In 1860, most cattle were eaten within a few hundred miles of their farm. By 1906, a cow could be born in Texas, slaughtered in Chicago and eaten in New York. Joshua Specht explains how the modern beef industry drove major changes in US agriculture, led by a handful of dominant firms that still hold sway today.

Uber drivers feel powerless on eve of IPO

When Uber goes public on 9 May its founder, Travis Kalanick, will most likely make several billion dollars. But the firm’s drivers are feeling increasingly poor, angry and powerless in the face of wage cuts and inadequate bonuses, as they tell Michael Sainato.

Revisiting the town destroyed by wildfire

Six months ago, the deadliest American wildfire in a century tore apart the California town of Paradise, killing 85 people. Alastair Gee and Dani Anguiano return to find the community still clinging together amid the wreckage.

Barry Lopez: ‘We’re living in emergency times’

Several years ago, the nature writer Barry Lopez was diagnosed with an aggressive form of cancer. That gives an even greater urgency to his message about the planet’s biodiversity crisis. “Something very big is going on the like of which we have never seen,” he tells Edward Helmore.

Opinion

Islamic State’s caliphate in Syria and Iraq may have collapsed, but the group has a new plan for the rest of the world, says Nicolas Hénin, beginning with Algeria and Sudan.

The paradox of the defeat of the caliphate is that as it has collapsed, the transformation of Isis into a global brand has been barely affected.

Sport

Manchester City lead the Premier League again ahead of the season’s last game, thanks to a 70th-minute screamer from Vincent Kompany, which sealed their 1-0 victory over Leicester.

James Harden scored 38 points on Monday to help keep the Houston Rockets in contention for the NBA playoffs: the Rockets’ 112-108 win over the Golden State Warriors levelled the Western Conference semi-final series at 2-2.

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