This table shows the main co-benefits and conflicts of key climate policies. It shows a simple rating based on what would happen if the technology or policy was deployed significantly more than at present.

Key: oo = large improvement; o = improvement; - = no significant change; x = deterioration; xx = large deterioration; ? = variable or uncertain

Note: ‘Water’ refers to both water demand and water pollution. Geo-engineering refers to sulphate aerosols and iron fertilisation of the oceans.

	Air	Water	Biodiversity	Energy security	Resources and waste	Cost
Energy efficiency	oo	oo	o	oo	o	oo
Material efficiency	o	oo	o	o	oo	oo
1st generation biofuels	x/-	xx	x	oo	x	-
2nd generation biofuels	-	-	-	oo	o	?
Renewable energy	oo	o	-	oo	?	?
Fuel switching (coal to gas)	o	-	-	x	-	-
Nuclear	oo	x	-	o	x	-
CCS	x	x	-	x	x	x
Forest protection	-	o	oo	-	-	x
Sustainable agriculture	o	o	o	o	o	-
Geo-engineering	xx	x	xx	x	-	x
Green lifestyle	oo	oo	oo	oo	oo	o

Although this table is only schematic, and grossly simplifies some very complex issues, it does show that some policies have a wide range of benefits, whereas others tend to be associated with conflicts. Four groups of policies can be identified:

Cutting waste: energy efficiency, resource efficiency and lifestyle change. Cutting waste avoids a wide range of impacts from resource extraction and use, including deforestation, pollution, landscape damage and the impacts of waste disposal. All of these options will cut fossil fuel use, thus reducing the damaging effects of air pollution, avoiding the environmental and safety impacts of oil, gas and coal extraction, and improving energy security, at the same time as saving money for households and businesses. Material efficiency also saves other scarce resources such as metal ores, water, phosphorous (for fertilisers) and land, thus protecting biodiversity and reducing the potential for international conflict, as well as cutting the costs and impacts of waste disposal. Lifestyle change is particularly important, because it can help to offset the rebound effect (where improved energy and material efficiency is outweighed by increasing consumption).
Low-carbon energy: bio-fuels, other renewables, nuclear energy and switching from coal to gas. Although these policies cut fossil fuel use, and so generally have the co-benefits of cutting air pollution, reducing fossil fuel extraction impacts and improving energy security, they also present a range of negative impacts, such as the landscape impacts of wind farms; the waste, proliferation and safety implications of nuclear power, and the land and water use problems of bio-fuels.
Agriculture and forest protection. Policies in these sectors have a very wide range of benefits and conflicts, and complex interactions between economic, social and environmental issues. There is tremendous potential to protect and enhance biodiversity through forest protection schemes, but there can be economic and social conflicts attached to funding the schemes and ensuring that communities are not displaced from their land. Similarly, climate-smart agriculture based on increasing soil carbon levels and reducing emissions from fertilisers could dramatically reduce the large environmental impacts of food production, but there are trade-offs between the use agrochemicals, which can increase yields and thus reduce deforestation from cropland expansion, or less intensive organic methods that reduce pollution and protect farmland biodiversity but may have lower yields, with implications for food security and food prices.
End of pipe and beyond: CCS (carbon capture and storage) and geo-engineering. Neither of these options harnesses any co-benefits, and both entail extra economic, environmental and energy costs. CCS carries an energy penalty of around 25%, increasing the impacts from fossil fuel extraction and decreasing energy security, though emissions of some air pollutants could be reduced. There could, however, be a role for CCS in conjunction with sustainable bio-fuels, where these negative fossil-fuel related effects would be absent although the energy penalty would increase the biofuel feedstock required. Geo-engineering could be even more damaging. The two most commonly advocated forms of geo-engineering - sulphate aerosols and iron fertilisation of the ocean - pose major risks to biodiversity. It is almost impossible to predict the impacts of such major intervention in the environment. Sulphate aerosol injection threatens to increase acid rain and have unpredictable impacts on rainfall patterns, and iron fertilisation could have drastic impacts on marine ecosystems.

By looking at the big picture, taking into account not just climate change but also all the other benefits and impacts of policy options, we can see that some policies are more promising than others. Cutting resource use – through energy and material efficiency coupled with demand reduction – tackles a multitude of different environmental problems at source, effectively ‘turning off the tap’ of environmental damage. CCS and geo-engineering, on the other hand, only try to tackle the problem of carbon emissions after they have already been created - just ‘mopping up the water’. They therefore fail to gain any co-benefits, and they also have serious negative impacts. Agriculture and forest policies have the potential to deliver major benefits for biodiversity and the environment, provided that the right safeguards are put in place to protect against economic and social conflicts. That leaves the diverse group of low carbon energy technologies - nuclear, bio-fuels, renewables and fuel switching. No energy source is impact-free: the policy challenge here is to ensure that the market chooses the ‘least bad’ technologies, and to look for ways of mitigating the impacts by good policy design.

Links to other co-benefits pages