almost universally unsustainable, and has resulted in rapidly declining water tables in many regions of the world. Future water demands from increasing population and agricultural consumption will likely climb between 4,500 and 6,200 cubic kilometers per year, hugely compounding the impacts of climate change, especially in arid regions.Widespread pollution. Agriculture, particularly the use of industrial fertilizers and other chemicals, has fundamentally upset the chemistry of the entire planet. Already, the use of fertilizers has more than doubled the flows of nitrogen and phosphorus compounds in the environment, resulting in widespread water pollution and the massive degradation of lakes and rivers. Excess nutrient pollution is now so widespread, it is even contributing to the disruption of coastal oceans and fishing grounds by creating hypoxic "dead zones," including one in the Gulf of Mexico. Given our current practices, future increases in food demand will dramatically increase water pollution and ecosystem destruction through agricultural effluent. Ironically, the fertilizer runoff from farmlands compromises another crucial source of food: coastal fishing grounds.Greenhouse gas emissions. Last, but certainly not least, land use is also one of the biggest contributors to global warming. Of the three most important man-made greenhouse gasses carbon dioxide, methane and nitrous oxide land use and agricultural practices, including tropical deforestation, emit 30 percent of the total. That's more than the emissions from all the world's passenger cars, trucks, trains and planes, or the emissions from all electricity generation or manufacturing. Compared to any other human activity, land use and agriculture are the greatest emitters of greenhouse gasses. The vast majority comes from deforestation, methane emissions from animals and rice fields, and nitrous oxide emissions from heavily fertilized fields. Yet, for some reason, agriculture has been largely able to avoid the attention of emissions reductions policies.The list of environmental impacts from agricultural land use goes on and on and clearly threatens human well-being and the health of the biosphere as much as global warming. In fact, in a recent paper in Nature, a number of us documented "planetary boundaries" where large-scale environmental changes could result in catastrophic tipping points. Of those changes, an equal number were tied to climate change and CO2 emissions as were connected to land-use and agriculture.From these newly revealed facts, it's clear that we must consider multiple inconvenient truths. The future of our civilization and our planet requires that we simultaneously address the grand challenges of climate change and land use, ultimately finding new ways to meet the needs of our economy, our security and the environment. Anything less will be a complete catastrophe.So, what are the solutions to the global land crisis? Here are just a few to start with.First, acknowledge the problem. Even in circles of well-informed scientists and agricultural experts, the notion that our land use and agricultural practices rival climate change as a global environmental threat comes as a big surprise. Clearly we need to have a larger international conversation about this issue, on par with the recent efforts of the climate change community and Al Gore, to give it the attention it deserves.Invest in revolutionary agricultural