In our ongoing effort to spotlight groundbreaking research and the brilliant minds behind it, we are excited to present a Q&A with Andrew Gougherty, a prominent Landscape Ecologist with the United States Department of Agriculture (USDA). With a keen focus on the intricate dynamics between ecosystems and their surrounding landscapes, Dr. Gougherty’s work is at the forefront of understanding how environmental changes impact biodiversity and ecological health.

In this exclusive interview, he delves into his recent research, shares insights on the challenges and opportunities in landscape ecology, and discusses the broader implications of his findings for conservation and land management. Join us as we explore the fascinating world of landscape ecology through the expertise of Andrew Gougherty.

It seems like trees are getting sick more often worldwide. What’s causing this increase in tree diseases?

There are multiple causes for the increasing accumulation of pathogens globally. First, many new diseases are the result of pathogens being introduced to new areas where they haven’t existed historically, mostly due to increasing international trade. Second, trees, and plants in general, are being planted in new regions, either for cultivation, forestry, aesthetics, etc., and are being exposed to new pathogens that don’t exist in their native ranges. Third, climate change and land use change can allow some pathogens to thrive which might increase the likelihood of them damaging trees. Finally, some of the increase in pathogen accumulation is likely due to better reporting and improved laboratory techniques to identify pathogens.

Why are pines, oaks, and eucalyptus getting more diseases? Does planting them all over the world make them more vulnerable?

Of the trees we looked at pines, oaks, and Eucalyptus species were among those that accumulated the most new pathogens over the past 20 years. There are probably several reason why this is the case. First, pines and oaks are very widely distributed in the Northern Hemisphere, so when their pathogens are accidentally transported between continents – for instance from Europe to North America or vice versa – these pathogens may be more likely to already have a suitable host present where they are introduced. Second, these tree genera, especially Eucalyptus, are widely planted outside their native ranges. When trees are grown outside their native ranges, they’re exposed to a suite of new pathogens some of which may spillover from their native hosts to these newly available hosts.

Local trees seem to get sick more than non-native ones, except in Latin America and the Caribbean. Why?

The focus of this paper was mostly on trees that are native to the northern hemisphere, so it was not surprising that Europe, North America, and Asia had the greatest disease accumulation. Most of the trees we assessed were not native to Latin America & the Caribbean, as a result, accumulation in this region was mainly on non-native hosts.

You’ve used a lot of data to figure out where and which trees are getting sick. Can you describe the process and how the information can be used?

Basically, the data I used in this study was put together by searching for reports of new pathogens in new areas or pathogens on new hosts that were documented in the scientific literature. I then went through as many reports as I could find and recorded what country the pathogens were reported in and which hosts were affected. From this, I determined the number of new pathogens in each country and on each host. As a next step, my hope is that this data will also be useful for identifying the role climate and land use change play on the emergence of new diseases, with the goal of being able to predict where new diseases may be most likely to emerge.

If tree diseases keep increasing, what are the broader implications for the environment and humans?

The real worry with new diseases accumulating is that a particularly damaging pathogen will emerge or be introduced to a new area. A lot of pathogens probably aren’t going to cause widespread devastation, but the really damaging ones can effectively eliminate their hosts from an area, which can reshape forest composition, and affect ecosystem function. With more and more diseases emerging in new areas, the odds of a really damaging disease emerging increases.

How is the changing climate messing with the health of trees?

Climate change is likely partially responsible for new disease outbreaks. Extreme, or anomalous, weather events can create unique conditions that can allow pathogens to thrive or can stress trees leading them to be less able to resist infection. It is difficult to determine if any particular disease emergence is due to climate change, but in aggregate we expect some pathogens to worsen with climate change.

Did anything in your research on tree diseases across 88 countries catch you off guard or challenge what we thought we knew?

The largest surprise was simply how fast new diseases are being reported – especially that the number is doubling about every 11 years. Some of these pathogens could pose real threats to forests and no global region is immune to these new pathogens.

How can we get better at spotting and tracking tree diseases, especially in less wealthy places that might not have good monitoring right now?

This is a difficult question because pathogens can have very subtle symptoms, and often it requires laboratory tests to accurately identify pathogens. It is likely that, even in wealthier counties, new pathogens can exist for years before they are observed and identified. Many new diseases are the result of introductions, so anything that can be done before pathogens have a chance to establish on the landscape, for instance by increasing surveillance at ports, are likely to pay off in the long term.

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