Since the world's first big environment conference in 1972, green issues have become woven into the political agenda and into consumer consciousness.
But as this snapshot shows, few problems have been resolved and some are worsening fast.
Ozone Protection: The 1987 UN Montreal Protocol outlawed chlorofluorocarbon gases (CFCs) that erode Earth's ozone layer, which protects the planet from cancer-causing solar rays. Further expansion of the Antarctic ozone hole has been halted, but full recovery is not expected until mid-century or later.
Climate Change: At the 1992 Rio Summit, the UN set up the Framework Convention on Climate Change. In 1997, the UNFCCC gave birth to the Kyoto Protocol, the only treaty to require specific cuts in greenhouse-gas emissions. But Kyoto has been outstripped by emissions by emerging giant economies which do not have such targets. UNFCCC parties have agreed to forge a new pact by 2015, taking effect from 2020. Time is short. Earth is on track for warming of 3.0 degrees Celsius (5.4 Fahrenheit) or more by century's end, gravely worsening perils from drought, floods, storms and rising seas.
Biodiversity: The Convention on Biological Diversity (CBD), another 1992 offshoot, has failed to make headway against species loss. The world badly missed a Millennium Development Goal (MDG) target of a significant reduction in the rate of biodiversity loss by 2010. Since 1980, the condition of coral reefs has declined by 38 percent. Loss of habitat, especially to agriculture, has in some places been more than 20 percent since the 1980s.
Oceans: Except for a few fisheries that are under good national control, fish stocks are suffering unprecedented depletion. In 2007, just seven percent of the output of global fisheries were certified by the Marine Stewardship Council, showing the products came from eco-friendlier sources. The oceans have 169 coastal "dead zones" and 415 coastal areas that suffer from eutrophication, meaning low levels of oxygen or excess nitrogen from fertiliser runoff.
Freshwater: Over the past 50 years, global withdrawals of groundwater have tripled in response to a surge in urban populations and demand from agriculture. Only 158 out of 263 river basins that cross national boundaries have agreements on cooperative management of the resource. Ninety-two percent of the world's water footprint comes from farming.
Energy: A massive increase in interest in renewables, helped by targets set in Europe especially, contrasts with the domination of fossil fuels, which accounted for 80.9 percent of energy supplies in 2009. Since 1992, solar energy has increased by nearly 30,000 percent, and wind by 6,000 percent, in output. But together with geothermal, they accounted for only 0.8 percent of the global total in 2009. Biofuels and waste-burning contributed 10.2 percent. Global investment in renewable power and fuels set a new record in 2010 of $211 billion, 540 percent more than 2004.
Deforestation: Since 1992, the world's primary forests have decreased by 300 million hectares (750 million acres), an area almost as big as Argentina. Deforestation is the third biggest source of global-warming gases. The good news is that reforestation is gaining ground in the nothern hemisphere, and there has been some progress towards offering financial incentives to protect native forests rather than cut them down. A 2006 UN initiative to plant at least a billion trees a year has reached more than double its target.
Pollution and Waste: Annual production of plastics has more than doubled in the past two decades to 265 million tonnes, half of which is used for one-off applications. Plastics decompose very slowly, creating a major long-term environmental hazard. On the other hand, the number of oil-tanker spills have declined over the past 20 years; lead in petrol, or gasoline, is close to being eliminated; and there is a worldwide treaty to curb the infamous "Dirty Dozen" persistent organic pollutants -- chemicals that biodegrade so slowly that they accumulate in the food chain. Also on the plus side, consumers are more sensitive to recycling, provided it is not too costly.
Source: Global Environment Outlook report 2012 by UN Environment Programme (UNEP); energy figures from 2011 report by Organisation for Economic Cooperation and Development (OECD) and International Energy Agency (IEA) and 2012 UNEP report.