Chapter 6: Land and a changing climate

The impacts of climate change are expected to become more intense in the coming years. They will challenge the way we manage land and more powerfully influence how land in some areas can be used.

A longer growing season and warmer temperatures may bring new opportunities but more extreme weather events (like droughts) are likely to seriously affect agricultural production and forestry.

The measures we take to reduce greenhouse gas emissions and adapt to a changing climate are also likely to influence land use. The effects can be direct, such as changes in management to reduce emissions from livestock or increase native trees. Indirect changes can also influence land use, like policy changes that shift markets and lead to more trees being planted.

The push and pull of global markets is currently the main driver of land use in New Zealand. Climate change, however, will play an increasingly important role as its impacts intensify. By the end of this century, the average global temperature is likely to be three degrees warmer than the pre-industrial temperature even if all current emission reduction commitments and goals are met by the international community (IPCC, 2018).

How quickly the climate changes depends on many factors, particularly the speed of the transition to net zero carbon dioxide emissions. The more the transition is delayed, the greater the changes to the climate and the magnitude of the impacts are likely to be (MfE & Stats NZ, 2020a).

Rising temperatures on land and in the ocean will translate into effects on land and how it can be used (IPCC, 2019). The climate has always shaped the types of ecosystems and land use that are possible in a given place, but it will increasingly influence the range of possible land uses in a particular area (Mendelsohn & Dinar, 2009). This will be felt most acutely where sea-level rise eliminates the possibility of certain land uses due to flooding, inundation, and salt water intrusion (MfE, 2020).

Higher temperatures, changes to rainfall, and more frequent and intense storms are likely to increasingly affect large areas of New Zealand’s landscape (MfE, 2018). This may narrow the areas where certain land uses are viable, or may make conditions suitable for other, new land uses.

Climate change is likely to affect land indirectly though policies and changes to land management that are designed to mitigate or adapt to the effects of climate change. These policies will shape land use by making some land uses more or less economically or socially attractive.

Changes in the magnitude and frequency of extreme weather events (like floods, droughts, and heatwaves) are projected to increase across much of the country. This will require us to adapt and make innovative responses (Ausseil et al., 2019a; Cradock-Henry et al., 2020; MfE, 2018). In many places, however, the changes will cause a threshold to be crossed where the current land use is no longer compatible with the new climate.

Drought can have significant impacts on land and the people who derive a living from it. Between 2007 and 2017 it is estimated that drought driven by climate change cost New Zealanders $720 million in insured damages and economic losses. This is six times the figure estimated for insured damages from increasing floods (Frame et al., 2018).

Changes to the frequency and intensity of droughts have been observed across New Zealand, and along with heatwaves, are expected to become more common and more extreme in many places as the climate continues to warm (MfE & Stats NZ, 2020a). The greatest increase in the frequency of droughts is expected to be in the North Island (MfE & Stats NZ, 2020a).

Irrigation allows farmers to grow crops that might not be viable under natural climatic conditions, and to alleviate the effects of a drought when it occurs. Increasing irrigation may solve the problem of drought in the short term, but extracting more water from rivers, lakes, and aquifers during droughts risks depleting these sources of water (MfE & Stats NZ, 2020b).

Considerable irrigation infrastructure is already available in inland Canterbury and Otago but much less so in the North Island (see figure 3). Models predict that in some parts of Canterbury, Otago, and Hawke’s Bay, rivers and streams would run dry if water users took out the full volumes they have been allocated (MfE & Stats NZ, 2020b).

At the other end of the spectrum, climate change is projected to increase the frequency and magnitude of intense rainfall, which can cause floods (MfE, 2018). In places where floods occur more often, changes in land management or even land use, may be needed as certain activities become unworkable.

We have changed and adapted the ways we use land in response to various driving forces. Climate change will challenge the sustainability of our production systems, and provide opportunities to adapt to, and even capitalise on some of the potential benefits.

Some climate impacts may be beneficial for farmers. Higher concentrations of carbon dioxide in the atmosphere may have a positive effect on plant growth and crop productivity in some cases (Rutledge et al., 2017). This is likely to lead to better plant growth and higher pasture yields (Ausseil et al., 2019b). The positive effects are also likely to be at least partially counteracted by losses from increased extreme weather events (Rutledge et al., 2017), drought, and a higher risk of heat stress for animals (Ausseil et al., 2019b).

Changes in management practices are anticipated as climate patterns shift. Fewer frosts and increased temperatures in the northern North Island for example may expand subtropical and tropical climates where a range of new crops could be grown commercially (Northland Regional Council, 2017). Wine growers could respond to a new climate by changing the varieties of grapes they grow, and farmers may alter the breed or species of their livestock. Some drought-tolerant grape varieties and pasture species are already being investigated and grown (Booth et al., 2020; Cradock-Henry et al., 2020).

Climate change is also projected to lengthen the growing season in New Zealand. (See indicator: Growing degree days.) This could increase overall productivity by increasing the growth of some crops and allowing for more crop cycles per year (Clothier et al., 2012).

A different land use or changing to a new crop may not align with a landowner’s previous experience, expertise, or personal preference – farming and forestry for example require very different skills (Cradock-Henry et al., 2020). Support and advice to deal with the challenges of climate change will become increasingly important as farmers are on the front line in tackling and responding to climate change (He Pou a Rangi Climate Change Commission, 2021).

Changes in the way we use land are underway to reduce emissions as well as the greenhouse gases that are already in the atmosphere. These include converting marginal farmland to native and plantation forest in the One billion Trees programme (MPI, 2020d). Options to reduce greenhouse gas emissions include lowering the density of dairy cows, sheep, and other livestock; improving animal performance; using less fertiliser; and breeding sheep that produce fewer emissions (BERG, 2018).

Policies to mitigate or adapt to climate change will also affect how land is used in the future. In many places local governments have created plans to reduce emissions, and manage the risks from sea-level rise and flooding. Most plans aim to reduce greenhouse gas emissions to zero by 2050, following the Paris Agreement and Zero Carbon Act timeline (Auckland Council, n.d.). Some have a longer timeframe like the 100-year plan to address coastal erosion in Hawke’s Bay (Bendall, 2018). These plans may force changes in land use or affect economic markets that cause changes in land use. Incentives to plant more native trees to store carbon, for example, could cause shifts in land use from agriculture to native forestry (Norton et al., 2020).