People once believed the planet could always accommodate us. That the resilience of the Earth system meant nature would always provide. But we now know this is not necessarily the case. As big as the world is, our impact is bigger.

In research released May 31, an international team of scientists from the Earth Commission, of which we were part, identified eight “safe” and “just” boundaries spanning five vital planetary systems: climate change, the biosphere, freshwater, nutrient use in fertilisers and air pollution. This is the first time an assessment of boundaries has quantified the harms to people from changes to the Earth system.

“Safe” means boundaries maintaining stability and resilience of our planetary systems on which we rely. “Just”, in this work, means boundaries which minimise significant harm to people. Together, they’re a health barometer for the planet.

Assessing our planet’s health is a big task. It took the expertise of 51 world-leading researchers from natural and social sciences. Our methods included modelling, literature reviews and expert judgement. We assessed factors such as tipping point risks, declines in Earth system functions, historical variability and effects on people.

Alarmingly, we found humanity has exceeded the safe and just limits for four of five systems. Aerosol pollution is the sole exception. Urgent action, based on the best available science, is now needed.

So, what did we find?

Our work builds on the influential concepts of planetary boundaries by finding ways to quantify what just systems look like alongside safety.

Importantly, the safe and just boundaries are defined at local to global spatial scales appropriate for assessing and managing planetary systems – as small as one square kilometre in the case of biodiversity. This is crucial because many natural functions act at local scales.

Here are the boundaries:

1. Climate boundary – keep warming to 1℃

We know the Paris Agreement goal of 1.5℃ avoids a high risk of triggering dangerous climate tipping points.

But even now, with warming at 1.2℃, many people around the world are being hit hard by climate-linked disasters, such as the recent extreme heat in China, fires in Canada, severe floods in Pakistan and droughts in the United States and the Horn of Africa.

At 1.5℃, hundreds of millions of people could be exposed to average annual temperatures over 29℃, which is outside the human climate niche and can be fatal. That means a just boundary for climate is nearer to 1°C. This makes the need to halt further carbon emissions even more urgent.

2. Biosphere boundaries: Expand intact ecosystems to cover 50-60% of the earth

A healthy biosphere ensures a safe and just planet by storing carbon, maintaining global water cycles and soil quality, protecting pollinators and many other ecosystem services. To safeguard these services, we need 50 to 60% of the world’s land to have largely intact natural ecosystems.

Recent research puts the current figure at between 45% and 50%, which includes vast areas of land with relatively low populations, including parts of Australia and the Amazon rainforest. These areas are already under pressure from climate change and other human activity.

Locally, we need about 20-25% of each square kilometre of farms, towns, cities or other human-dominated landscapes to contain largely intact natural ecosystems. At present, only a third of our human-dominated landscapes meet this threshold.

3. Freshwater boundaries: Keep groundwater levels up and don’t suck rivers dry

Too much freshwater is a problem, as unprecedented floods in Australia and Pakistan show. And too little is also a problem, with unprecedented droughts taking their toll on food production.

To bring fresh water systems back into balance, a rule of thumb is to avoid taking or adding more than 20% of a river or stream’s water in any one month, in the absence of local knowledge of environmental flows.

At present, 66% of the world’s land area meets this boundary, when flows are averaged over the year. But human settlement has a major impact: less than half of the world’s population lives in these areas. Groundwater, too, is overused. At present, almost half the world’s land is subject to groundwater overextraction.

4. Fertiliser and nutrient boundaries: Halve the runoff from fertilisers

When farmers overuse fertilisers on their fields, rain washes nitrogen and phosphorus runoff into rivers and oceans. These nutrients can trigger algal blooms, damage ecosystems and worsen drinking water quality.

Yet many farming regions in poorer countries don’t have enough fertiliser, which is unjust.

Worldwide, our nitrogen and phosphorus use are up to double their safe and just boundaries. While this needs to be reduced in many countries, in other parts of the world fertiliser use can safely increase.

5. Aerosol pollution boundary: Sharply reduce dangerous air pollution and reduce regional differences

New research shows differences in concentration of aerosol pollutants between Northern and Southern hemispheres could disrupt wind patterns and monsoons if pollutant levels keep increasing. That is, air pollution could actually upend weather systems.

At present, aerosol concentrations have not yet reached weather-changing levels. But much of the world is exposed to dangerous levels of fine particle pollution (known as PM 2.5) in the air, causing an estimated 4.2 million deaths a year.

We must significantly reduce these pollutants to safer levels – under 15 micrograms per cubic metre of air.

We must act

We must urgently navigate towards a safe and just future, and strive to return our planetary systems back within safe and just boundaries through just means.

To stop human civilisation from pushing the Earths’s systems out of balance, we will have to tackle the many ways we damage the planet.

To work towards a world compatible with the Earth’s limits means setting and achieving science-based targets. To translate these boundaries to actions will require urgent support from government to create regulatory and incentive-based systems to drive the changes needed.

Setting boundaries and targets is vital. The Paris Agreement galvanised faster action on climate. But we need similar boundaries to ensure the future holds fresh water, clean air, a planet still full of life and a good life for humans.

We would like to acknowledge support from the Earth Commission, which is hosted by Future Earth, and is the science component of the Global Commons Alliance

Steven J Lade, Resilience researcher at Australian National University, Australian National University; Ben Stewart-Koster, Senior research fellow, Griffith University; Stuart Bunn, Professor, Australian Rivers Institute, Griffith University; Syezlin Hasan, Research fellow, Griffith University, and Xuemei Bai, Distinguished Professor, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Social Security is in trouble.

The retirement and disability program has been running a cash-flow deficit since 2010. Its trust fund, which holds US$2.7 trillion, is rapidly diminishing. Social Security’s trustees, a group that includes the secretaries of the departments of Treasury, Labor, and Health and Human Services, as well as the Social Security commissioner, project that the trust fund will be completely drained by 2033.

Under current law, when that trust fund is empty, Social Security can pay benefits only from dedicated tax revenues, which would by that point cover about 77% of promised benefits. Another way to say this is that when the trust fund is depleted, under current law, Social Security beneficiaries would see a sudden 23% cut in their monthly checks in 2034.

As economists who study the Medicare and Social Security programs, we view the above scenario as politically unacceptable. Such a sudden and dramatic benefit cut would anger a lot of voters. Unfortunately, the actions necessary now to avoid it – like raising taxes or cutting benefits – aren’t getting serious consideration today. But we believe there are strategies that could work.

Where the money for benefits comes from

Roughly 67 million Americans, most of whom are 65 or older, receive Social Security benefits. The agency disburses more than $1 trillion annually. It’s the government’s largest single expenditure, constituting nearly 20% of the total federal budget.

Social Security is funded by a payroll tax of 12.4% on wages split equally between workers and employers. Self-employed people pay the entire 12.4%. This payroll tax applies to earnings up to $160,200 as of 2023. The government increases this cap annually based on increases in the National Average Wage Index – a measure that combines wage growth and inflation. The program also receives about 4% of its revenue from a tax on Social Security benefits, though not everyone who receives them has to pay this tax.

Social Security tax revenue stayed relatively flat after 1990. But the costs of the program rose sharply in 2010, in part because of early retirements in response to the Great Recession.

Social Security spending has recently been growing more rapidly because of a wave of baby boomer retirements, which added to a decline in the number of workers per retiree.

Costs of the program are expected to further exceed the money that’s coming in, which will continue to drain the trust fund, according to the program’s trustees.

Barring immediate action by the government, the trust fund’s exhaustion is only a little more than a decade away. And yet few members of Congress seem willing to do something about it. For example, Social Security reform was not even on the table during the 2023 negotiations over the debt ceiling and spending cuts.

Trust fund

Where did the trust fund, which helps cover the program’s costs, come from?

While the Social Security program was collecting surpluses from 1984 to 2009, that extra money funded other spending – keeping other taxes lower than they would have been otherwise and partially covering the budget deficit.

During Social Security’s years of surplus, the excess revenues were credited to the trust fund in the form of special-issue government bonds that yielded the prevailing interest rates. When those bonds are needed to pay for Social Security expenses, the Treasury redeems them.

Those bonds are components of the government’s $31.4 trillion gross debt.

Last reformed during the Reagan administration

Reducing the benefits current retirees receive would be extremely unpopular. Likewise, people now in the workforce who are nearing retirement would certainly object strongly if they were told to expect lower benefits in retirement than they have been promised throughout their careers.

The last time the government made big changes to Social Security was in 1983, during the Reagan administration, when the government enacted reforms that slowly reduced benefits over time. These changes included raising the full retirement age, a change that is still being phased in. Because of those changes, workers born in 1960 or later cannot retire with full benefits until age 67 – two years later than the original retirement age.

The 1983 reforms also included increases in the Social Security payroll tax rate from 10.4% in 1983 to 12.4% by 1990, and for the first time levied federal income taxes on higher-income retirees’ benefits. Workers bore the burden of the payroll tax increases and higher-income retirees bore the burden of the tax on benefits.

Those changes bolstered the program’s finances, but they no longer suffice.

The bipartisan 2001 Commission to Strengthen Social Security tried – and failed – during George W. Bush’s presidency to get Congress to enact reforms to shore up the program’s finances. There’s been no momentum toward resolving the problem since then.

4 principles

We believe that policymakers and lawmakers need to follow four principles as they consider how to move forward.

1. The program should be self-funded in the long run so that its annual revenues match its annual expenses. That way the many questions that arise related to trust fund accounting and whether Social Security tax revenues are being used for their intended purposes would be eliminated.

2. The reform burden should be shared across generations. Current retirees can share the burden through a reform that reduces the cost-of-living adjustment. Today’s workers can share the burden through an increase in the cap on income subjected to Social Security taxes so that 90% of total earnings are taxed. Continued gradual increases in the retirement age to keep pace with anticipated longevity gains would also be borne by current workers.

3. The government should make sure that Social Security benefits will be adequate for lower-income retirees for years to come. That means reforms that slow the benefit growth of future retirees would be designed to affect only higher-income retirees.

4. Any changes to Social Security should help constrain the future growth of federal spending, given the current and projected growth in the budget deficit.

Advantages of ending the delay

It appears that the U.S. – citizens and elected officials included – are deferring serious debate on this urgent matter until the trust fund’s depletion is imminent. That’s unwise. Acting sooner rather than later would leave more options available to gradually resolve the program’s financial shortfalls.

Ending this procrastination would also give the millions of people who rely on Social Security benefits, taxpayers and businesses more time to prepare for any changes required by overdue reforms.

Andrew Rettenmaier, Executive Associate Director of the Private Enterprise Research Center, Texas A&M University and Dennis W. Jansen, Professor of Economics and Director of the Private Enterprise Research Center, Texas A&M University

This article is republished from The Conversation under a Creative Commons license. Read the original article.