Marginal improvements to agricultural soils around the world would store enough carbon to keep the world within 1.5C of global heating, new research suggests.

Farming techniques that improve long-term fertility and yields can also help to store more carbon in soils but are often ignored in favour of intensive techniques using large amounts of artificial fertiliser, much of it wasted, that can increase greenhouse gas emissions.

Using better farming techniques to store 1% more carbon in about half of the world’s agricultural soils would be enough to absorb about 31 gigatonnes of carbon dioxide a year, according to new data. That amount is not far off the 32 gigatonnes gap between current planned emissions reduction globally per year and the amount of carbon that must be cut by 2030 to stay within 1.5C.

The estimates were carried out by Jacqueline McGlade, the former chief scientist at the UN environment programme and former executive director of the European Environment Agency. She found that storing more carbon in the top 30cm of agricultural soils would be feasible in many regions where soils are currently degraded.

McGlade now leads a commercial organisation that sells soil data to farmers. Downforce Technologies uses publicly available global data, satellite images and lidar to assess in detail how much carbon is stored in soils, which can now be done down to the level of individual fields.

“Outside the farming sector, people do not understand how important soils are to the climate,” said McGlade. “Changing farming could make soils carbon negative, making them absorb carbon, and reducing the cost of farming.”

She said farmers could face a short-term cost while they changed their methods, away from the overuse of artificial fertiliser, but after a transition period of two to three years their yields would improve and their soils would be much healthier.

She estimated it would cost about $1m (£790,000) to restore 40,000 hectares (99,000 acres) of what is currently badly degraded farmland in Kenya, an area that is home to about 300,000 people.

Downforce data could also allow farmers to sell carbon credits based on how much additional carbon dioxide their fields are absorbing. Soil has long been known to be one of Earth’s biggest stores of carbon, but until now it has not been possible to examine in detail how much carbon soils in particular areas are locking up and how much they are emitting. About 40% of the world’s farmland is now degraded, according to UN estimates.

Carbon dioxide removal, the name given to a suite of technologies and techniques that increase the uptake of carbon dioxide from the air and sequester the carbon in some form, is an increasing area of interest, as the world slips closer to the critical threshold of 1.5C of global heating above pre-industrial levels.

Arable farmers could sequester more carbon within their soils by changing their crop rotation, planting cover crops such as clover, or using direct drilling, which allows crops to be planted without the need for ploughing. Livestock farmers could improve their soils by growing more native grasses.

Hedgerows also help to sequester carbon in the soil, because they have large underground networks of mycorrhizal fungi and microbes that can extend metres into the field. Farmers have spent decades removing hedgerows to make intensive farming easier, but restoring them, and maintaining existing hedgerows, would improve biodiversity, reduce the erosion of topsoil, and help to stop harmful agricultural runoff, which is a key polluter of rivers.

Civil rights groups and Democrats reacted angrily to the US supreme court decision in favor of the Colorado web designer Lorie Smith, who argued she had a first amendment right to refuse to provide services for same-sex marriages. Critics of the court’s decision say it ushers in a new era of prejudice in America.

“This ruling on LGBTQ+ rights by the Maga-right activist wing of the supreme court is a giant step backward for human rights and equal protection in America,” said the Democratic Senate majority leader, Chuck Schumer, in a statement. “We will continue to fight to ensure that all Americans, including LGBTQ+ Americans, have equal protection under the law.”

The progressive Democratic congresswoman Rashida Tlaib called for term limits of justices on the conservative-dominated supreme court which has now ushered in a series of decisions rolling back well-established rights, such as overturning federal protections on abortion and affirmative action.

“End lifetime appointments for supreme court justices. Enforce a binding code of ethics. Expand the court,” Tlaib posted on Twitter.

The New York congressman Ritchie Torres said: “Scotus invokes religious liberty to license discrimination against LGBTQ people. The LGBTQ community might be the first victim of the supreme court’s decision but it won’t be the last. Injustice anywhere is a threat to justice everywhere.”

Civil rights groups were also vocal in their shock and warned of the impact on LGTBQ+ communities across the US who see it as opening the way for people and businesses to legally refuse services to LGBTQ+ people.

“This decision will have a devastating ripple effect across the country by creating a permission structure, backed by the force of law, to discriminate and endanger LGBTQ+ people and trans youth who are already so at risk,” said the Rev Paul Brandeis Raushenbush, president and chief executive of the Interfaith Alliance.

“Discrimination under the guise of religious freedom is not just unconstitutional, but antithetical to our values,” added Darcy Hirsh, director of policy and advocacy at the group. “Just as people are free to explore matters of faith and personal conscience, people should also be free to express their sexual orientation and gender identity without fear of discrimination or harm.”

The Human Rights Campaign, one of America’s largest LGBTQ advocacy organizations, called the ruling in the case, known as 303 Creative LLC v Elenis, “unprecedented” and a decision that “will have sweeping and harmful impacts on the LGBTQ+ community and is a dangerous step backwards”.

“Our nation has been on a path of progress – deciding over the course of many decades that businesses should be open regardless of race, disability or religion. People deserve to have commercial spaces that are safe and welcoming,” said the organisation’s president, Kelley Robinson, in a statement.

But the Republican former vice-president Mike Pence, who is running for the 2024 Republican presidential nomination and popular with rightwing evangelicals, praised the court’s decision.

“Religious freedom is the bedrock of our constitution,” he said, “and today’s decision reminds us that we must elect leaders who will defend that right and appoint judges who support religious freedom.”

Kristin Waggoner with Alliance Defending Freedom, the group that brought Smith’s case, said the court had “rightly reaffirmed that the government can’t force Americans to say things they don’t believe”.

In a six to three vote, split down ideological lines, the highest court ruled that the first amendment prohibits Colorado from forcing the website designer to create expressive designs with which the designer disagreed.

In the majority opinion, Justice Neil Gorsuch wrote that the free speech amendment in the constitution “envisions the United States as a rich and complex place where all persons are free to think and speak as they wish, not as the government demands”.

Gorsuch also invoked George Orwell, writing that “if liberty means anything at all, it means the right to tell people what they do not want to hear”.

The liberal justice Sonia Sotomayor responded to Gorsuch, writing that “the majority’s repeated invocation of this Orwellian thought policing is revealing of just how much it misunderstands this case”.