Understanding and supporting the urban forest becomes increasingly important with urbanisation and now with COVID lockdowns

Trees and woodlands generally, and the urban forest in particular, have never been more significant and important to both human society and to the environmental functioning of our planet. However, take a look across the world and forests are being felled and cleared and landscapes from Brazil and Indonesia to the Australian outback are burning. Soils and fertility are eroded and washed off the land to pollute the seas, oceans and fisheries. With this scenario and global human populations rising and temperatures too, is it surprising that we experience major problems? I would argue that we are not entering a post-COVID situation when the current pandemic begins to ease, but more realistically are entering a new phase of the longterm human-nature paradigm. It has been asserted by some commentators that the present COVID pandemic is at least to a degree, a consequence in part of human disruption of planetary ecosystems and ecological processes. Indeed, it is hard to not see the logic in this view of the 2020 crisis. In so many ways our expanding human population has triggered mass extinction and global environmental degradation to stress ecological systems and to weaken human resistance to new disease and contagion. With trees generally, and urban trees in particular, worldwide climate change and other environmental stresses are combining with globalisation to trigger massive spread of diseases and pests beyond their established ranges. The use of commercially grown clonal varieties of tree-stock approved and exported across continents (as in the case of common ash, Fraxinus excelsior) is a major worry and a potentially spectacular ecological “own goal”. Faced by mass plantings of clonal trees a pest or disease may prove rampant until it comes across plants with a degree of genetically in-built resistance. Environmental disruption also includes problems such as atmospheric fallout of acid rain and now nitrogen oxides, which, acting as mass fertiliser have the potential to disrupt the mutualistic fungal associations of great trees – especially their root-based mycorrhizal symbionts. Yet we are increasingly aware that these mutualistic fungi in the roots as mycorrhizas but in the above-grown plant tissues too, are the basis of the good health of many trees. Disrupted or displaced, the loss of these fungi may lead to decline and death of the trees. Returning to COVID and global lockdown, one major observation to emerge from the situation has been the importance of green spaces and especially trees and woods, in promoting and enhancing human health and wellbeing. Particularly, in poorer areas (in terms of socio-economic deprivation and low environmental quality) trees and woods bring huge benefits to local people who are fitter, happier, and healthier. It has even been shown that children’s educational performance can be enhanced by Arboricultural Journal 2020, VOL. 42, NO. 4, 187–189 https://doi.org/10.1080/03071375.2020.1860540