Five million metric tons of carbon dioxide equivalent.

This is the target – at least for now – that is likely to drive
"smart growth"-style land use planning in California over the next few years. It's the tentative reduction target that the California Air Resources Board has assigned to the land use sector in order to help meet the state's greenhouse gas (GHG) emissions reduction goals by 2020.

CARB adopted the target in its AB "Climate Change Scoping Plan" in mid-December.

First, it's not a very large percentage of the overall statewide reduction target of 174 million metric tons of carbon dioxide equivalent (MMTCO2E).

Second, it's not nearly what environmentalists asked for. They wanted a reduction of between 11 and 15 MMTCO2E.

Third, it is still a pretty big number. As near as I can tell, meeting this target will require a reduction in vehicle miles traveled (from the current levels, not projected 2020 levels) of around 3-4%, which would require a considerable shift in land use patterns.

And fourth, it actually is not the final number. CARB punted to the soon-to-be-appointed "Regional Targets Advisory Committee" called for in SB 375 (see CP&DR, November 2008, September 2008). The committee will to do an analysis of each region in the state and come up with a target for that region. The total reductions could be more or less than 5 million metric tons. But if it's less, then CARB will have to come up with other savings somewhere else. So the battle over the target is far from finished – and it's likely to stretch well into 2010, when the regional numbers must be finalized.

Let's take a step back and look at just exactly what 5 million metric tons means in the real world of planning and development.

Right now, Californians have more than 35 million vehicles, and they drive about 330 billion miles a year. Obviously, that's more than any other state. On a per-capita basis, however, California does pretty well. Annual per-capita vehicle miles traveled (VMT) in California is about 9,000 miles, or about 24.6 miles per day. This ranks California 11th out of the 50 states in VMT efficiency. By contrast, per-capita VMT is about 10,200 miles in Texas and 11,300 miles in Florida. Still, all this driving represents a significant amount of greenhouse gas emissions – somewhere around 135 million metric tons per year, or slightly less than a third of the state's current total of around 460 million metric tons.

The problem is that VMT is expected to go up in the future – both in absolute numbers and per capita – and it has to go down in order for the state to meet the AB 32 targets. Forecasts for VMT for 2020 range between 380 billion and 430 billion miles, and the higher number is a much more likely "business as usual" scenario. This kicks the GHG emissions up to around 180 billion metric tons.

Under AB 32, the state is expected to realize significant savings in vehicle-related GHGs from two other sources – better fuel efficiency for the vehicles themselves (32 million metric tons) and lower carbon content in the gasoline (15 million metric tons). But that still won't be enough to meet the state's goal. Hence the 5 million metric ton total to be extracted from changing land use patterns.

So how much driving do we have to eliminate?

If nothing else were to change, VMT would have to go down 11 billion miles per year from the current number – about 31 million miles per day. That's the equivalent of taking more than 1 million vehicles off the road completely in California.

Alternatively, it's the equivalent of everybody in California – 40 million or so vehicles – driving about 1 mile less per day.

Obviously, lots of people are locked into current driving patterns because they live in residential subdivisions accessible only by car. Others will probably increase their driving if they move to distant areas in order to buy houses, such as the Central Valley and Southern California's high desert. So that puts an enormous amount of pressure on infill development to deliver driving reductions.

In essence, infill is going to have to offset all the increased VMT from new greenfield development and deliver a reduction of 31 million miles driven every day from current levels.

Does this mean the end of greenfield development in California? Obviously not. There's too much land in play, too big a market and too many expectations – by landowners, developers, and local governments – for greenfield projects to go away. But the regional targets, combined with new SB 97 requirements to study a project's contribution to climate change, will put enormous pressure on greenfield projects to minimize their carbon footprint.

And because even the most carbon-light greenfield development will create an increase in greenhouse gases, there will be an enormous amount of pressure on infill projects to create greenhouse gas savings. Inevitably, if AB 32 is the driving force, regional planning agencies will have to stack huge densities at every serious transit stop, and even in nodes and activity centers not heavily served by transit in order to reduce VMT (even if congestion increases). Infill areas could conceivably serve as "mitigation banks" for greenfield projects.

Of course, if the enviros have their way, the target will be double or triple the 5 million metric tons per day. And because the land use target is currently squishy, it's possible that other sectors who anticipate having a tough time making their target will try to push for more savings from the land use sector.

Which leads us, inevitably, to the politics of the Regional Targets Advisory Committee, which will recommend the actual land use target for each region. Senate Bill 375 says that the committee – which is scheduled to be appointed this month – is to be essentially a land use stakeholder committee that includes representatives from the metropolitan planning organizations and the air districts; from cities, counties, and local transportation agencies; and from homebuilding groups, environmental organizations, planning organizations, environmental justice organizations, affordable housing organizations, and other groups.

Senate Bill 375 envisions a nerdy, technical task for the Regional Targets Advisory Committee, which is supposed to pass judgment on the modeling that will forecast possible GHG savings from land use in each region, as well as growth predictions and jobs-housing balance forecasts. The committee is supposed to make its recommendations to CARB by September.

No matter how technical the task is on paper, however, the targets committee inevitably will be enmeshed in a political tug-of-war among the usual land use suspects – local governments, homebuilders, environmentalists – over the numbers. Local governments and homebuilders will probably argue in favor of 5 million metric tons at most – and maybe less. Environmentalists will probably continue to argue for double or triple that number. Given the history of land use politics in Sacramento, it is hard to see how this committee will break through the usual logjam to have a meaningful discussion about how to shape the future of California's growth.