Science videos

Ag Matters videos provide short and simple introductions to the science behind climate change, agricultural greenhouse gases and soil carbon.

Climate change basics

Human activities are causing climate change by changing the delicate balance of the atmosphere, and agriculture is contributing to the problem. You can read more about this on the Climate change basics topic page. 

In this short video, learn how human activities are causing climate change by changing the delicate balance of the atmosphere. How is agriculture contributing to the problem?


Duration: 2:42

Kia ora. We’re here to talk about climate change – how it works, and how it relates on-farm.

We’ll also reveal New Zealand’s biggest contributor to climate change. It might not be what you think, and it’s rather close to home.



[Is she looking at us?]

Our atmosphere is a magnificent cocktail of gases, water vapour and particles that constantly mix and mingle. It gives us our oxygen, protects us from radiation from the sun, and controls our weather. It’s a delicate balance, and all life depends on it.

But we’re doing things down here which are really upsetting the balance up there. Human activities are rapidly increasing the concentration of greenhouse gases in the atmosphere. They’re called greenhouse gases because they trap the heat and warm the planet. The main greenhouse gases that we produce are carbon dioxide, nitrous oxide and methane. Globally, carbon dioxide is the most important because it stays in the atmosphere a very long time.

Here’s what’s going on.

Incoming solar radiation warms up the surface of the Earth. The Earth’s surface then sends this heat back through the atmosphere and most of it goes out into space. But some of this heat is trapped by greenhouse gases, and this extra heat warms up the atmosphere.

So, the more greenhouse gases we emit into our atmosphere, the more it’ll warm up and affect our climate.

And it’s already having a big impact. Earth’s temperature has warmed by about one degree Celsius since humans started using coal, oil and other fossil fuels. Globally, 18 of the hottest 19 years on record have occurred since the year 2000.

Here in New Zealand, temperatures are about one degree hotter than they were a century ago. We’re seeing more extreme weather and that’s before we talk about rising sea levels, melting glaciers and polar ice. 

Indeed, the evidence is compelling.

As our climate in New Zealand changes, it might not be possible to farm in the same ways or the same places as we do now. A couple of degrees of warming might not seem like much, but it has a big impact on crop and pasture growth, and on pests and diseases. More extreme weather also creates bigger problems.

Now it might surprise you to learn that New Zealand’s biggest current contribution to this isn’t carbon dioxide at all.

Nope. It’s methane from animals.


What the?

You can find out more about how methane affects climate change in our next video.

Produced by the New Zealand Agricultural Greenhouse Gas Research Centre. Funded by the New Zealand Government

Why does methane matter?

Learn why emissions of methane, an important but widely misunderstood greenhouse gas, must be addressed if New Zealand is to meet its greenhouse gas emissions-reduction targets. You can learn more about this on the Reduce methane emissions goals page.

In this short video, learn where methane comes from, how it contributes to climate change, and why it's vital that steps are taken to reduce emissions.


Duration: 3:21

So how exactly is methane produced, and how does it contribute to climate change? There are a lot of different stories out there, but this is how it actually works.

Methane comes from several places, including wetlands, landfills, forest fires, agriculture and fossil fuel extraction. But here in New Zealand, the largest proportion by far is belched out by livestock.

[What, all livestock?]

[Not us, surely!]

It’s perfectly natural. Microbes in the fore-stomach of ruminant animals, like cows and sheep, break down the pasture the animals have eaten and produce methane. And, well, it has to come out somehow.

Great … but it breaks down though, right?

Well, it’s true that methane released into the atmosphere breaks down much faster than other greenhouse gases like carbon dioxide. But while it exists, it has a big impact. Tonne for tonne, methane is actually many times more effective at absorbing heat than carbon dioxide.

An emission of methane will mostly disappear from the atmosphere within 50 years. But while it’s up there, every molecule traps lots of heat. An equivalent emission of carbon dioxide traps less heat, but stays around much, much longer. Thousands of years in fact.

We’ll show you what it looks like. Let’s say filling up the board with symbols is equivalent to a certain temperature increase.

I’m emitting carbon dioxide into the atmosphere every year. Because CO2 takes so long to break down, every emission adds to the warming caused by previous emissions. The amount of CO2 increases over time, and the effects become bigger and bigger.

Okay. I’m emitting methane into the atmosphere. Each emission makes a big contribution to warming, but fortunately we’re not emitting nearly as much methane as we are carbon dioxide.

So as we do this, Gavin is going to rub out the methane symbols to show they break down at a much faster rate in the atmosphere, and I’m going to continue emitting at the same rate.

So if we keep emitting the same amount of methane, the amount in the atmosphere levels out, because the new emissions by and large just replace the previous emissions that have now disappeared.

[So, what’s the problem?]

[New burps replace the warming caused by old ones.]

But, we’ve increased our methane emissions a lot over the past century. This has pushed temperatures up already, and globally they’re still going up.

If we keep emitting methane at the current rate, that will keep the atmosphere a lot warmer than it used to be.

So, at a minimum, if we want to stop additional warming from methane we need to reduce the amount of emissions.

They don’t have to be stopped completely, but the more that they’re reduced, the less warming is caused and the better for the climate. How far could we go?

[I don’t mind a change of diet!]

Climate change is a complex challenge. But we’ve already achieved heaps thanks to some clever Kiwi innovation and farmers becoming more and more efficient. But there is more that we can do. New technology will play its part, but there’s more that you can do now. Find out what in our next video.

Produced by the New Zealand Agricultural Greenhouse Gas Research Centre. Funded by the New Zealand Government.

How to reduce emissions

Learn some of the steps New Zealand farmers can consider in an effort to reduce emissions of the main agricultural greenhouse gases. You can learn more about this on the Reduce methane emissions and Reduce nitrous oxide emissions goals pages.

This video explains the steps New Zealand farmers can consider in an effort to reduce emissions of the main agricultural greenhouse gases, methane and nitrous oxide, while maintaining a profitable business.


Duration: 3:03

Farmers have been asking: what can I do to reduce emissions on my farm? Well, there are three gases we need to reduce: carbon dioxide, nitrous oxide, and methane. But on-farm, it’s particularly about the last two. Lots of small steps can add up to make a big difference.

The good news is that combined greenhouse gas emissions from New Zealand agriculture are no longer going up, thanks to farmers’ efforts to become more and more productive and efficient over the years. As a result, the greenhouse gases emitted per unit of product are going down.

Without all this great work, emissions from agriculture in New Zealand would be about 30 percent higher than now, to produce the same amount of food.

[But there’s a lot more of us now.]

[And a lot fewer of us!]

But we need to reduce emissions, not just keep them steady. There’s no magical formula here, but there are several things that can be done on farms right now – and some will have other benefits too.

You know your business better than anyone, so you’re in the best place to work out which of these are achievable.

Here’s what some farmers are doing already, that you might want to consider for your farm.

First, find out what your farm’s greenhouse gas emissions are and include them in your planning. Depending on the farm, it might be that some of those options can save you time, and money.

In a nutshell, methane emissions are related to the total amount of dry matter eaten. Nitrous oxide emissions depend on the total amount of nitrogen going through your farm via feed and fertiliser. So, what steps can be taken to change these quantities, while still running a profitable business?

Look carefully at the feeds used. Can you use feeds with lower nitrogen or higher energy content to get animals to market quicker? Would a less-intensive system work for you? It might be reducing fertiliser inputs and stocking rates, changing the ratio of your stock type, or once-a-day milking.

You could try using precision technologies for improving the amount and timing of your fertiliser application.

Look at the balance between individual animal performance and stocking rate. Could you run slightly fewer animals and focus more on getting the most out of each animal to keep production up?

You could also consider the balance of your land use to reduce livestock emissions. Many farmers are now integrating trees onto their less productive land, and there is Government support to help do this.

For some farms, diversifying some of the land use to cropping or horticulture could reduce overall emissions and dependence on one income stream.

Rest assured, you’re not alone in your efforts. Scientists are working hard on new solutions, with some very promising results. Some of them are being trialled already. In the future, it’s likely we’ll be able to breed low-methane animals or use inhibitors and vaccinations to reduce the amount of methane that animals belch out.

We’re all working towards the same goal, and any small step is a step in the right direction.

Remember to check out our website for lots more information. Thanks for watching.

Produced by the New Zealand Agricultural Greenhouse Gas Research Centre. Funded by the New Zealand Government

Nitrous oxide basics

Where does nitrous oxide come from, what is its effect on the atmosphere, and what are some of the options researchers are exploring that farmers and growers might be able to use to reduce emissions? You can learn more about this on the Reduce nitrous oxide emissions goals page.

In this short video, Dr Cecile de Klein of AgResearch explains where nitrous oxide comes from, its effect on the atmosphere, and some of the options researchers are exploring that farmers and growers might be able to use to reduce their nitrous oxide emissions.


Duration: 5:15

Most NZ farmers are in the business of growing plants.

either to feed livestock or people, or produce seeds.

Applying nitrogen helps plants to grow.

But it's no secret that too much nitrogen can lead to nitrates entering our streams, rivers and lakes.

What you might not know is that nitrogen in the soil also produces a greenhouse gas that's far more potent than carbon dioxide or methane.

In a moment we'll show you what you can do to reduce emissions of this gas, But first let's see what's going on in the soil.

There's no 'Planet B', this is what we've got and we need to leave it in a better place for our children and our children's, children's children.

So that they can enjoy life as we know it. That's really what drives me.

I've been working on nirous oxide emissions for over thirty years now.

It's a very potent greenhouse gas, it's about 300 times more effective at trapping heat than carbon dioxide

It's also a long lived gas. It stays in the atmosphere for over 100 years. But its warming effect can stay on for centuries after that.

Nitrous oxide is a gas that's produced naturally in the soil by microbes.

They use nitrogen that is in the system to convert to nitrous oxide.

Nitrogen gets introduced into farming systems through fertiliser, clover, supplementary feed and animal urine.

Soil microbes use that nitrogen that's in the soil to transfer it into a form that plants can use.

But not all of the nitrogen is used by plants. Some of it sits in the soil, mainly as nitrate.

And that can then leach into the waterways or convert into nitrous oxide.

So, tonne for tonne nitrous oxide is many times more effective at trapping heat than carbon dioxide.

Fortunately we produce a lot less of it. But nitrous oxide still accounts for around 12% of NZ's total greenhouse gas emissions.

There must be something we can do about it right? Let's see what the scientists are up to.

Some of the solutions they're looking into are using different plants to utilise the excess nitrogen in the soil.

And there are some new technologies on the horizon.

One example is looking at some new nitrification inhibitors that can reduce nitrous oxide emissions.

Using plantain also appears to hold some promise for reducing both nitrate leaching and nitrous oxide emissions.

Partly that's because there's less nitrogen going through the animal and there's less nitrogen in the urine.

But there also seems to be a positive effect of the plant roots on the soil microbes that will reduce nitrous oxide emissions.

Work is still ongoing and we still need to understand the mechanism behind this.

And also how plantain can be used best and how can we maintain it in the system. They're all big questions still to be answered.

So a number of solutions are showing real promise, but there are things you can try on your farm now that might make a difference. Let's take a look.

Key things to do are to consider whether you can reduce your fertiliser input.

There are more and more technologies out there that can help you with precision fertiliser application.

Put it in places that need it where nitrogen is low. These technologies are coming or are already out there.

If you're a livestock farmer consider reducing stocking rate.

If you're able to produce the same amount of product with fewer animals,

then that means the animals don't need as much maintenance feed and that means you don't need as much nitrogen inputs such as fertiliser or supplementary feed.

Which means less N in the system and that will have a positive effect on nitrate leaching as well. So it's a win win scenario.

In cropping systems the main source of nitrous oxide is the fertiliser that is applied to the crops.

So fertiliser timing rates and scheduling is key in terms of minimising nitrous oxide emissions.

And making sure that most of the nitrogen is used for plant growth.

Right now there isn't one single solution for reducing nitrous oxide emissions.

The most reliable option is to cut back the amount of nitrogen hitting your soil – by lowering stock numbers, reducing supplementary feeds or using less fertiliser.

Reducing nitrogen in your soil will also reduce nitrate leaching.

Scientists are working hard to find solutions to reduce nitrous oxide.

You can keep up to date with all the developments on

Soil carbon basics

Learn where soil carbon comes from, why it’s important, and why increasing New Zealand’s soil carbon levels isn’t easy. You can learn more about this on the Maintain or increase soil carbon goals page.

In this video, Professor Louis Schipper from the University of Waikato explains where soil carbon comes from, why it’s important, and why increasing New Zealand’s soil carbon levels isn’t easy.


Duration: 5:27

Healthy soil contains plenty of carbon, nutrients and moisture to help crops and pasture thrive.

The carbon in soil is also an important factor in climate change.

Globally, there's more carbon in soils than all land based plants and the atmosphere combined.

So taking even a bit more carbon out of the atmosphere and into the soil could be good for the climate as well as your farm.

But losing soil carbon has the opposite effect.

Now despite what you might of heard, it isn't that easy to increase soil carbon in NZ. Why is that?

I think that farmers have a very complex operation.

They're trying to juggle, how do we maintain production, look after our animals and also have this broader responsibility of looking after the environment as well.

One of the difficulties of farming is that there is inevitably some losses of greenhouse gas emissions.

All organisms produce carbon dioxide through a process called respiration.

But that's only one half of the equation.

The other half of the equation is plants taking carbon dioxide out of the atmosphere through photosynthesis

into their leaves, down into their roots and it eventually ends up in the soil.

And so, we have these two big processes going on at the same time.

A small difference between the two, results in an accumulation of carbon in the soil or a loss of carbon from the soil.

Our key job is to find ways to increase the amount that is captured and decrease the amount that is released into the atmosphere.

So when we think about this balance of carbon dioxide going down into the soil and being re-released,

we have these two big processes of photosynthesis and respiration.

If a soil is bare, so there's no plants growing on it, you've reduced the capture of carbon dioxide, and you're reducing the amount that's going into the soil.

The micro organisms in the soil keep decomposing or breaking down the carbon that is in the soil and re-releasing it into the atmosphere.

So when you think about a bare soil you've effectively stopped carbon dioxide being captured but the micro organisms are continuing to pump out carbon dioxide.

Avoiding soils being bare and not having active photosynthesising plants on them, is something that you should look to do.

Another way that we're exploring is whether there are different species that we can add into the pasture mix,

that will have more or different kind of roots penetrating through the soil and increasing the carbon content of the soil.

We've been looking at things like plantain, chicory, tall fescue and it's really going to be about what plants are best where.

It's early days yet but there's some promising leads that increasing the diversity of pastures can increase the amount of carbon in soil.

In NZ we're really lucky because we've got really forgiving soils, we have year round growth, and a great climate.

What has happened is that we've built up large amounts of carbon in our soils in comparison to many other countries.

Additionally, we tend to farm in a way that there's always vegetation on the surface and we're not continuously cropping large areas.

As a result we've got really large amounts of carbon in most of our soils around NZ.

It can be quite hard to increase the amount of carbon that you have in your soil. There are practices out there that might be able to help.

And those practices will not only benefit the amount of carbon dioxide that's in the atmosphere and increase the amount of carbon that's in soil.

But if you can increase the amount of carbon or just maintain what you've got then you've got a healthier soil.

That's going to support the vegetation above it better, and it's going to have better environmental outcomes.

It might make that soil more resilient to external disturbances like droughts.

Keeping the amount of carbon that you have in soil is simply good farming practice.

The aim is to draw carbon into our soil and keep it there.

But NZ soils are already naturally high in carbon, so adding more is a lot harder than some other parts of the world.

And even though we grow a lot of grass, that doesn't tell us our soil carbon is increasing.

In fact, latest data suggests it's been steady at best in flat land and declining in peat soils.

It seems to have increased in hill country soils but we don't know if that's continuing.

So what's important right now is holding on to the soil carbon that we have.

There's lots of research underway to explore how we can do this.

It's looking at actions like avoiding bare soils and planting diverse pastures to find out how they affect soil carbon under NZ's different farm types.

You can find out more about this research and NZ's different soil carbon levels at

Published: December 2, 2021