Already at risk from countries imposing penal "carbon" taxes at the border, a greater threat to New Zealand exporters could lie in the perceptions of overseas consumers about the sustainability of their goods.

That view is held by the New Zealand Institute of Economic Research (NZIER), an independent non-profit group of economic analysts.

"Although New Zealand may not be explicitly targeted by border taxes in the short term, there remain some longer term risks to our exporters from the increased global focus on the environmental impacts of trade," NZIER said today.

AgResearch's former head of climate and environment, Harry Clark, who is setting up a science centre for agricultural greenhouse gases, recently warned of moves in countries such as France and Germany to impose penal tariffs at the border on produce from countries regarded as making too little effort to reduce their greenhouse gas emissions.

The NZIER said today there were a number of countries talking about introducing such border taxes on imports from countries that have soft policies to tackle climate change.

"This is a risk to New Zealand's exports, but overseas consumer perceptions of the sustainability of goods produced in New Zealand are a greater threat," it said.

The emissions trading scheme (ETS) being debated in Parliament and the Government's 2020 emissions target had sparked concern from people who believed New Zealand should be doing more to tackle climate change.

So far, no border taxes have been imposed to compensate for domestic carbon prices, but they have featured prominently in discussions around United States climate change policy and the next phase of the European Union's ETS.

Such taxes could be permissible under World Trade Organisation rules, and even if they were not carefully designed, it could take years to resolve any subsequent trade dispute.

There are relatively few countries so far with carbon prices in place.

"As long as the carbon burden that New Zealand's competitors face is lower than the one that New Zealand firms face, a punitive border tax makes no sense," the report said.

It was the carbon cost differential between New Zealand and its competitors that mattered, not the cost in New Zealand.

The US had made clear that any border tax there would be targeting big countries such as India and China. The rules approved by American legislators exempted from border taxes countries which emit less than 0.5 percent of total global greenhouse gas emissions and account for less than 0.5 percent of US imports of a specific category of goods. "Based on current proposals, it seems unlikely that New Zealand exporters would be targeted by punitive border taxes in the immediate future," the report said.

But though New Zealand may not be explicitly targeted by border taxes in the short term, there remained potential for such taxes and other environmental trade barriers to be used in a protectionist way, and to even trigger trade wars.

Even if no border taxes were imposed, consumer preferences on sustainability mattered, as had been seen in the so-called "food miles" debate, and talk of the environmental benefit of meat-free diets.

"If New Zealand's agricultural exports are perceived as being unsustainable, even if in reality they are energy-efficient, then our market share in key export markets is at risk," the NZIER said.

"New Zealand exporters need to continue monitoring offshore consumer trends and investing in demonstrating their sustainability credentials".