<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world's forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited,” </span><span class="" style="font-family: Verdana; font-size: 14px;"><b class="">and </b></span><span class="" style="font-size: 14px; font-family: Verdana;">“Overall, our review reveals the potential for amplified tree mortality due to drought and heat in forests worldwide” (Allen et many al 2010).</span><span class="" style="font-size: 14px; font-family: Verdana;"> </span></p><div class=""><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;"> “Our results reveal a complex geographical mosaic of species-specific responses to climate change-driven drought pressures on the Iberian Peninsula, with an overwhelmingly predominant trend toward increased drought damage” (Carnicer et al 2011).</span></p></div><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Climate-driven forest die-off from drought and heat stress has occurred around the world, is expected to increase with climate change and probably has distinct consequences from those of other forest disturbances” (Anderegg et al 2012).</span></p><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“If the vapour-pressure deficit continues increasing as projected by climate models, the mean forest drought-stress by the 2050s will exceed that of the most severe droughts in the past 1,000 years. Collectively, the results foreshadow twenty-first-century changes in forest structures and compositions, with transition of forests in the southwestern United States, and perhaps water-limited forests globally, towards distributions unfamiliar to modern civilization.” (Williams et al 2012).<o:p class=""></o:p></span></p><p class="MsoNormal"><span class="" style="font-size: 14px;"><span class="" style="font-family: Verdana;"> </span><span class="" style="font-family: Verdana;">“Warming seems already to be altering the duration and frequency of drought in some regions of the globe, a trend that will probably become clearer as global warming proceeds” (Overpeck, 2013).</span></span></p><div class=""><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Contrary to the expectation that surviving trees have weathered severe drought, the hydraulic deterioration demonstrated here reveals that surviving regions of these forests are actually more vulnerable to future droughts due to accumulated xylem damage.”(Anderegg et al 2013).</span></p></div><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Tree mortality in relatively undisturbed old-growth forests across the West has risen even when not triggered by wildfires or insect infestations” (Funk et al, 2014).</span></p><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Although disturbances such as fire and native insects can contribute to natural dynamics of forest health, exceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability” (Millar and Stephenson, 2015).</span></p><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Here, we reveal temporally increasing tree mortality across all study species over the last three decades in the central boreal forests of Canada, where long-term water availability has increased without apparent climate change-associated drought. …. Our results suggest that the consequences of climate change on tree mortality are more profound than previously thought” (Luo and Chen 2015).</span></p><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Although most of the boreal forests have retained the resilience to cope with current disturbances, projected environmental changes of unprecedented speed and amplitude pose a substantial threat to their health” (Gauthier et al 2015).</span></p><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Drought and heat-induced tree mortality is accelerating in many forest biomes as a consequence of a warming climate, resulting in a threat to global forests unlike any in recorded history,” and “we conclude with high certainty that today's forests are going to be subject to continued increases in mortality rates that will result in substantial reorganization of their structure and carbon storage” (McDowell and Allen, 2015).</span></p><p class="MsoNormal"><span class="" style="font-family: Verdana; font-size: 14px;">“Estimates of megadrought probabilities based on precipitation alone tend to underestimate risk. Furthermore, business-as-usual emissions of greenhouse gases will drive regional warming and drying, regardless of large precipitation uncertainties” (Ault et al 2016).</span></p><p class="MsoNormal"><span class="" style="font-size: 14px;"><span class="" style="font-family: Verdana;">“</span><span class="" style="font-family: Verdana;">Warm droughts, one of the most important global climate changes, have recently occurred in North America, Africa, Europe, Amazonia, and Australia, with major effects on terrestrial ecosystems, carbon balances, and food security [1, 2]. Warm droughts can alter ecosystemic structure, composition, and services, such as carbon sequestration, biological conservation, and water regulation [3–6]. Prolonged droughts or heat can kill trees [7]. Recent studies have indicated that forest mortality induced by rising temperatures and increased drought have rapidly increased around the world during the past decade [6–9]” (Zhang et al 2017).</span></span></p><p class="MsoNormal" style="line-height: 18px;"><span class="" style="line-height: 21px; font-family: Verdana; font-size: 14px;">Finally, the Forest Service has made the same point, succinctly, deep in its own outlook for drought's impact: </span><span class="" style="font-family: Verdana; font-size: 14px;">“In essence, a survivable drought of the past can become an intolerable drought under a warming climate” (p.50, Vose et al, 2016).</span></p><p class="MsoNormal">—————————————————————————————————————————————————————————————————————</p><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><span class="">“</span><span class="" style="font-size: 14px;">Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence."<br class=""><br class="">Barnovsky et al. Approaching a state shift in Earth’s biosphere. Nature Volume 486, 07 June 2012<br class=""><br class="">doi:10.1038/nature11018</span></div></div></div><div class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">————————————————————————————————————————————————————————————————————————</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">“Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence."<br class=""><br class="">Barnovsky et al. Approaching a state shift in Earth’s biosphere. Nature Volume 486, 07 June 2012<br class=""><br class="">doi:10.1038/nature11018</div></div></div>
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