Before the 1992 summit, Brazil’s President Color told me that 65 heads of state were waiting to learn whether President Bush would attend the conference before committing to participate.  President Bush went, and world leaders (plus 10,000 journalists) followed, with important results. Rio built awareness about humanity’s growing environmental impact, inspired a generation of activists and entrepreneurs, and concluded major global treaties.
The whiff of politics was omnipresent at that first gathering, as it will be this year.  When Fidel Castro concluded his speech -- largely an attack on the United States -- President Bush applauded. Asked how he could explain his response, Bush said, “we were all allotted only 6 minutes. I didn’t think he could do it.” 

For those of us involved in the 1992 conference, the anniversary is bittersweet. We have not slowed, yet alone reversed, the increasing pace of ecological destruction. Greenhouse gas emissions worldwide are more than 20 percent higher than they were in 1992, when nations first committed to reduce emissions. The planet has lost an additional 270 million acres of forest—an area twice the size of France. The world continues to consume natural resources at an unsustainable pace.

From floods to wildfires to famine, we are already witnessing the serious, adverse implications of unsustainable economic activity. We have yet to fully grasp these implications, but one thing is clear: the ability of our natural systems to sustain human civilization will come into question in just the next few years and decades. To prevent the looming crises of resource scarcity, climate change, and ecosystem collapse, we must shift the way economies value and protect natural resources.

Yet, especially in recent years, there are important signs of progress. Brazil has reduced deforestation in the Amazon more than 75 percent since 2004.  China and Germany lead the world in renewable energy. Korea is trying to win the race to develop and export green technologies. India is betting on solar and wind power to lift many rural poor out of poverty.

Around the world, people today are far more likely than in 1992 to believe that sound environmental policies actually bolster economic growth, rather than harm it. The personal experience many have had with these policies offers proof positive: Well-designed energy efficiency standards for vehicles, appliances, and buildings, for example, reduce air pollution and carbon emissions, save money, improve energy security, and raise living standards. Investments in technology innovation can accelerate the pace of resource protection by doing more with less – and by reducing the cost of alternatives to resource extraction, such as renewable energy. Policies that encourage more intensive agriculture – using drip irrigation, for example - can increase crop yields and improve farm incomes while reducing soil erosion, runoff, wetlands loss, and deforestation. Though some of these ideas – like pollution taxes - may remain controversial in the United States, the U.S. is increasingly the exception rather than the norm.

Nations across the world better understand today that solutions depend on harnessing the creativity, energy, determination, and capital of the private sector. At the first Earth Summit, poor nations clamored for more foreign aid. Today, they want more private investment and more trade. This revolution in thinking was barely imaginable in 1992.  

World leaders need to capitalize on this progress and take bold strides to address increasingly urgent planetary threats.

For the first time, nations should set clear, ambitious and measurable objectives for sustainable growth. Compelling goals are a precondition for success, as any business leader knows.  U.N. Secretary General Ban Ki-moon’s proposal to ensure universal access to cleaner energy, double renewable energy production, and double energy efficiency improvements by 2030 offer a good starting point. Similar goals are required in other sectors.

Nations also need to change the way they measure progress. The World Bank estimates that one third of the wealth of low-income nations lies in their “natural capital” – their rivers, forests, grasslands, wetlands, and estuaries. Exploiting these resources for short-term gain is not progress; it’s more akin to raiding a retirement portfolio to pay current expenses. Likewise, economic policies must encourage investments in innovation -- we are only beginning to tap the power of technology to tackle global challenges.

World leaders should ensure that any country that marshals the political will to take ambitious action receives technical support from the international community. Several decades ago, the international community created a network of experts to spread modern agricultural practices, the so-called green revolution; millions applied this know-how and escaped poverty. Today, a similar effort is needed to promote clean energy policies and know-how around the world with a comparable aim. Efforts like the UN’s Sustainable Energy for All are a big step in the right direction, but need more support and emphasis from the international community.

Twenty years ago, we had to invent the policy tools and institutions required for sustainability. We have largely accomplished that. What is missing now is the political will and vision to use those tools to grow responsibly. It is arguably the greatest leadership question of our time.

Reilly, who served as EPA Administrator under George H. W. Bush, headed the U.S. delegation to the 1992 Rio Earth Summit. He is chairman of the ClimateWorks Foundation.