It's not unusual for parents to worry about the next generation and the future planet they'll inherit, but new research suggests having children doesn't necessarily make you any 'greener' as a person - quite the opposite, in fact.

A new study in Sweden has found that even those who really care about the environment often end up having their deck of priorities re-shuffled by the realities of parenthood.

After all, there's only so much time and energy available in a single day, and children have a way of sapping up a lot of those limited resources.

Comparing adult parents to adult non-parents in Sweden, researchers found households made up of the former tend to emit more carbon dioxide from transportation, food, heating, and electricity.

Ultimately, the team found two-adult households with children were responsible for over 25 percent more carbon emissions than two-adult households without children.

"Our findings suggest that having children might increase CO2 emissions both by adding to the population and by increasing CO2 emissions from those choosing to have children," the authors write.

While adding another human to the planet in this day and age will inevitably increase carbon emissions, especially in wealthier nations, by how much exactly is still up for debate, and currently, only a small fraction of adults choose not to have children because of environmental reasons.

This means there are many parents out there who consider themselves quite 'green' and who list the environment as a top priority, even though their behaviour isn't quite matching up.

"Becoming a parent can transform a person – he or she thinks more about the future and worries about future risks imposed on their children and progeny," explains economist Jason Shogren from the University of Wyoming (UW).

"But, while having children might be transformational, our results suggest that parents' concerns about climate change do not cause them to be 'greener' than non-parent adults."

This is one of the first rigorous studies on whether parents behave 'greener' than other adults. But it's still an open question, and the current findings will need to be verified in other nations and in larger sample sizes.

Previous research has provided mixed evidence on whether parenthood changes environmental attitudes, preferences, and behaviours, but the new study reevaluates the subject with a unique dataset, including an impressive 4,000 Swedish households.

Across all major household expenditures, the findings reveal a "substantial gap" in carbon emissions between parents and non-parents, especially in regards to transportation and food.

The results might be surprising, given how accepted climate change is in Sweden – the nation has a sizeable carbon tax that many people are happy to pay – but it's a good reminder that even with the best of intentions, parents can sometimes overlook the bigger impact of their actions for more immediate concerns.

This isn't to say it's entirely their fault, either. It may simply be about time and energy, although this is currently just one theory.

Reports on time usage in Swedish households reveal that out of all people, parents with small children have the least leisure time, and that's true even in a nation with generous parental leave. That could be making a big difference.

Carbon-intensive goods are usually convenient and cheap, the authors explain, which makes them particularly tempting to parents. When you're juggling the demands of a family, driving to the grocery store might be simpler than taking public transport or biking. Whereas pre-prepared food containing red meat might be convenient, and in some cases even cheaper.

Figuring out what's driving this emissions gap between adults is essential. The world isn't about to stop having children, so policies that alleviate some of the stress parents with young children are facing could allow families the time and money to better reduce their carbon footprint in the future.

For instance, if food really is an environmental issue in these households, then perhaps government subsidies for meat substitutes will go a longer way towards reducing emissions. Just as government policies for breastfeeding may reduce our reliance on formula milk, which produces a shocking amount of carbon emissions.

Still, there are other explanations, other than time and convenience. It may be stemming from the children themselves.

"Altruistic parents' consumption may also be impacted by the child's immediate preferences for carbon-intense consumption, such as a taste for red meat, flights to family-friendly resorts, and so on," the authors write.

"Children may of course also be concerned about the environment, which in turn may affect household consumption. Even though children in the Nordic countries have been found to be more environmentally concerned than their parents, there is a substantial gap between their attitudes and actions."

While the research took place in just one country, the authors think their findings are relevant to many other nations around the world.

"If we're finding these results in Sweden, it's pretty safe to assume that the disparity in carbon footprints between parents and non-parents is even bigger in most other Western countries," argues UW economist Linda Thunstrom.

The study was published in PLOS ONE.