Excessive mass, large frontal cross sections, 4WD, off road tyres and poor aerodynamics all contribute to higher fuel consumption and emissions. SUVs should be seen as yet another pointless automotive gimmick, continuing the trend towards more wasteful modes of transport.

The air you breath
Below is a comparison between the Toyota Corolla and Land Cruiser with figures from the VCA database (2003).  The land cruiser is more polluting in every category. It is estimated that around 400 New Zealanders [1] and 900-2000 Ausralians [2] are killed each year from vehicle exhaust.

Vehicle	Fuel, city cycle L/100km	CO2 (g/km)	CO (g/km)	PM10 (g/km)	NOx (g/km)	Noise (dB)
L' Cruiser Petrol	21.5	387	2.0	N/A	0.09	72
L' Cruiser Diesel	11.5-15.8	250-340	0.7	0.059-0.078	0.52-0.57	73-75
Corolla Petrol	8.4-11.1	159-198	0.45-0.47	N/A	0.02-0.08	69-71
Corolla Diesel	7.2-7.9	153	0.19-0.24	0.032-0.037	0.39-0.45	71-72

Climate change
Carbon dioxide emissions are directly proportional to fuel consumption. The higher the fuel consumption, and the greater the impact on climate change. For the facts on climate change please refer to the IPCC or the climate change hotmap.

Australia has the highest per capita greenhouse emissions in the world, over 27 tonnes per year (data from the UNFCC). New Zealand's emissions are also high by international standards at 14 tonnes/person/yr, compared to the E.U. average of 10.1.  45% of NZ's CO₂ emissions are from transport, the highest percentage in the OECD.

Diesel exhaust
Many SUVs (and some cars) sold in New Zealand and Australia run on diesel. Diesel engines are slightly more energy efficient than petrol engines of the same size, but produce more particulate, sulfur dioxide and nitrous oxide emissions. Ignore the rants by Alistair Sloan in the NZ Herald, and look up the emissions data yourself.

Unfortunately a double standard in the Euro-I through Euro-IV emission regulations has lead to the promotion of the image of a "clean" diesel. Euro-IV diesel cars are allowed to emit three times as much nitrous oxide and carbon monoxide as Euro-IV petrol cars. In practice the actuall difference is at least a factor of six.

In 2006 no diesel car came anywhere near meeting the minimum emissions standards in California. In 2003 the ABC ran a decent story on the subject of Diesel emissions in Australia, though nobody seems to have paid attention.

[1] "New Zealand evidence of health impacts of transport", National Health Comitee, (2002)
[2] "Health impact of transport emissions: Economic cost", BTRE working paper 63, (2005)
[3] "Australasian impacts of climate change", IPCC Working group II, Cambridge Uni. Press, (1998)