Saving the world’s ash forests calls for international cooperation now

Abstract

Ash forests in North America and Eurasia are rapidly being lost to two invasive alien species: Emerald Ash Borer and Chalara Ash Dieback Fungus. We assert here that better regulatory policy and science-based intervention can help slowing losses. To this end, we recommend an international consortium for coordinating science-based intervention.

Population genomics of the emerging forest pathogenNeonectria neomacrospora

“…and elm (Ulmus spp.) have declined (Brasier and Buck, 2001;Semizer-Cuming et al, 2018). During the first half of the 20 th century, Chestnut blight (Cryphonectria parasitica) devastated American chestnut forests in eastern North America killing, an estimated 3.5 billion trees after its accidental introduction from Asia (Liu and Milgroom, 2007).…”

Invasive Populations of Emerald Ash Borer <em>Agrilus planipennis</em> Fairmaire, 1888 (Coleoptera: Buprestidae) in Saint Petersburg, Russia: a “Hitchhiker”?

“…Yet, there is evidence that a proportion of European F. excelsior individuals across populations exhibits certain tolerance/resistance to ADB, providing the basis for future selection, breeding and propagation [17,18]. However, the proportion showing high resistance to ADB is low, estimated in a range between 1% and 5% of individuals [10,19,20]. Consequently, ex situ conservation and resistance breeding programs have been initiated in many European countries, providing a promising perspective to mitigate the damaging effects of ADB in the long-term.…”

The viability of a breeding programme for ash in the British Isles in the face of ash dieback

“…We do not yet know if the breeding of F. excelsior for resistance to both ADB and EAB is biologically possible from standing genetic variation. Dealing with this combined threat will need a great deal of international collaboration (Semizer-Cuming, Krutovsky, et al, 2019). Further research is needed to determine variability and heritability of EAB resistance in F. excelsior and whether or not there is a trade-off between ADB and EAB resistance.…”

“…What this means for the viability of current F. excelsior populations in the field under EAB pressure is not yet known. The invasive ranges of H. fraxineus and EAB now overlap in the region of Russia between Moscow and the border with Belarus, providing a natural experiment on the combined effect of the two threats (Musolin et al, ; Semizer‐Cuming, Krutovsky, et al, ). Any breeding programme for co‐occurrence of resistance to two very different threats is likely to be challenging.…”

“…Long‐term policy decisions about a newly established pathogen must also take into account possible future threats. In the case of ADB, ash populations are also threatened by the emerald ash borer (EAB), Agrilus planipennis , which is currently found near Moscow in Russia, with fears of it spreading further westwards (Musolin, Selikhovkin, Shabunin, Zviagintsev, & Baranchikov, ; Semizer‐Cuming, Krutovsky, Baranchikov, Kjӕr, & Williams, ; Straw, Williams, Kulinich, & Gninenko, ). This beetle has killed millions of ash trees in North America since its accidental introduction in the late 1990s, leaving American ash species, including F. pennsylvanica and F. americana , critically endangered (Jerome, Westwood, Oldfield, & Romero‐Severson, ; Westwood, Oldfield, Jerome, & Romero‐Severson, ).…”