Climate change: the biggest environmental challenge of our time.

It is impossible to escape the ongoing climate change debate. A quick google search of “climate change” when writing this blog generated 136 news articles from over the past 24 hours. It is clearly a very talked about issue and for good reason. It is now common knowledge that if we continue on the current path, then over the coming decades there will be higher average temperatures, rising sea levels, more frequent extreme weather events and changes in rainfall patterns. This is obviously simplistic and there could be other major effects as well.

In the news recently there has been some concern about potential slow down of the Atlantic oceanic currents which could have disastrous consequences. It could cause dramatic temperature shifts across the globe as well as having detrimental affects on marine life. Gone is the commonly held acceptance of the view “why worry, the effects won’t be seen for 50-100 years so it won’t affect me”. Aside from the callousness of this view, the effects of climate change are already being observed and yes in New Zealand as well. Temperature and rainfall changes are already being observed around the country. As a country with an economy heavily dependent on agriculture (generating a casual $37 billion per year) this may be seen as a significant threat. Or is it?

It all comes down to the details. Obviously there are a lot of unknowns about the impacts of climate change not only for agriculture but also generally. To try to predict some of these future impacts, a handy free report was released by the Ministry for the Environment. Basically when just looking at the effects on agriculture it is a mixed bag; both potentially positive and also negative impacts and it depends on the region. Generally speaking the east of the country will experience more drought whilst the west will be more prone to flooding.

Overall we are likely to see an increase in pasture production with arable crops also benefiting from increased carbon dioxide and warmer temperatures. Certain areas such as Canterbury may struggle due to more frequent droughts and less water for irrigation. Under a high carbon dioxide emissions scenario, New Zealand average temperatures are likely to skyrocket by 2090.

When it comes to the general population, the topic of plant diseases is pretty niche. “Plants get diseases?” some might ask. In fact they are extremely important in a country that is agriculturally savvy and prides itself on its unique biodiversity. The New Zealand native Kauri are under threat by (you guessed it) an extremely nasty plant disease known as Phytophthora.

Another disease that the general public may find relevant is myrtle rust that has arrived recently which affects pohutukawa and rata among others. If we look a little closer at myrtle rust we might ask where did it come from and why did it only arrive just recently? One widely held belief is that it arrived through strong winds from Australia. In fact just before it arrived there was a rather large cyclone that sped down the east coast of Australia which then hit the North Island of New Zealand. Speaking of climate change, didn’t we just say that it is causing more extreme weather events? Maybe this is speculation and the cyclone along with myrtle rust may have arrived regardless but it is an interesting idea. When we merge both plant diseases and climate change, we may encounter a recently published article. In this article, they are specifically looking at the effects of drought on plant diseases which is highly relevant to New Zealand.

The idea of a disease triangle has been well established, whereby for a plant to become infected by a pathogen three factors must be present: a susceptible host, a disease causing microbe and a favorable environment. Drought, being a factor in the host’s environment, is a very difficult thing to study as it is complex, with effects being dependent on timing and it also affects diseases in different ways. For much of the agricultural industry it is likely that growers can move out of areas that become uneconomic or grow different crops and therefore adapt to some of the effects of climate change. However, for the forestry industry, the trees they plant today may not be harvested for 30 years or more so planning becomes vital.

The most significant impact of drought is likely be on the soil environment so it will affect soil borne diseases the most. For half of the diseases that the authors investigated, the impacts of drought depended on its timing. Increasing drought events are expected in summer with climate change and this had the effect of increasing the damage caused by the disease due to plant stress.

An obvious solution may be to extend areas of irrigation to reduce the impact of drought. This may be one solution but it would increase the cost of production and in areas like Canterbury, water may become a scarce resource so other solutions are also required.

There is a lot of diversity among plant diseases as to their ability to resist drought. Although some diseases will be negatively affected by drought, the overall effect appears to be a negative one for New Zealand agricultural production. This is important to know as it allows us to plan for the future and make the most of the situation. Perhaps this will lead to further research both on breeding programmes for drought resistance as well as strategies for managing higher disease levels.

Research also may tell us which crops may benefit from the impacts of climate change so that we move away from susceptible crops to ones that actually thrive under new conditions. As we can see, not all the impacts of climate change are talked about and maybe that with such an all encompassing beast as climate change there are many other issues out there that are important to everyone but have not seen the light of day…yet.

The author Lewis Braithwaite is a postgraduate student in the Postgraduate Diploma in Applied Science. He wrote this article as part of his assessment for ECOL 608 Research Methods in Ecology.

Reference

Wakelin, S. A., Gomez-Gallego, M., Jones, E., Smaill, S., Lear, G., & Lambie, S. (2018). Climate change induced drought impacts on plant diseases in New Zealand. Australasian Plant Pathology, 1-14.