Assessing the economic and conservation impacts of the pine marten, a recovering predator, non-native grey squirrels, and forest land management

灰松鼠已被证明是世界上最具破坏性的外来入侵物种之一。灰松鼠吃树上的树皮，对林业造成严重破坏，并通过松鼠痘病毒的竞争和传播，在英国大部分地区导致当地红松鼠灭绝。这对英国林业产业和保护工作的影响是巨大的。据估计，每年因森林破坏和相关控制工作而造成的损失高达4000-5000万英磅，其中至少100万英磅用于英格兰北部和苏格兰的红松鼠保护，那里的红松鼠尚未灭绝。到目前为止，还没有成功的方法来长期控制(也没有真正根除)灰松鼠种群。到目前为止，防止对树木的损害在很大程度上依赖于华法林的使用，然而，将于2015年9月撤回使用华法林作为植物保护产品的批准。对商业落叶林业造成的巨大且日益严重的经济损害对英国景观和农村经济活动的构成具有重大的长期影响。由于灰松鼠、沙拉拉对灰烬和气候变化构成的综合威胁，林地所有者(包括Confor成员、项目第一合作伙伴)现在质疑试图在英国种植任何主要硬木树种的可行性。英国大部分地区失去了红松鼠，这让许多英国公众无法体验到与一个与它们有很强文化联系的物种的互动。事实上，除了少数几只数量不多、管理严密的红松鼠外，红松鼠现在几乎完全不在英格兰和威尔士。它的未来取决于公共资金的持续支出和承诺的非政府组织(特别是RSNE，第二号项目合作伙伴)的活动。一个主要的担忧是，如果维持灰松鼠控制的资金不能持续，那么迄今为止通过诱捕和射杀灰松鼠在保护红松鼠方面取得的进展将会失去。Sheehy博士最近发现，爱尔兰本土松貂的恢复和传播导致了灰松鼠数量的大幅下降，但红松鼠并没有减少，这既为博士生提供了解决方案的希望，也为他们提供了一个特殊的跨学科培训机会，以解决与林业、农村经济和保护密切相关的基本生态问题。松貂的种群几乎已经灭绝，苏格兰的种群近年来显著恢复，现在距离英格兰边境只有几英里远，这意味着英格兰从北部自然重新殖民迫在眉睫。威尔士的保护工作也正在由VWT(项目合作伙伴3号)进行。松貂在英国大陆的恢复和蔓延，为解决灰松鼠造成的问题带来了前所未有的希望。然而，食肉动物种群的恢复将不可避免地带来挑战，特别是当一个物种在缺席多年后返回时。几代人以来，土地管理者已经习惯于生活在捕食者匮乏的环境中，在这种环境中，某些做法很容易维持，因为捕食者稀少、不存在或可以受到法律控制。类似地，野生猎物种群可能会变得“捕食者幼稚”，在有天敌的情况下形成不可持续的行为模式和生殖产出。在这方面，随着松貂被鼓励恢复，将需要一段时间的调整期，在此期间，人类和野生动物种群都将适应更自然的环境。当捕食者种群的恢复导致或威胁给其他利益攸关方造成损失，或要求土地管理人改变做法时，不可避免地会出现冲突。

Grey squirrels have proved to be one of the world's most damaging invasive alien species. Grey squirrels cause profound damage to forestry by eating bark from trees, and have driven native red squirrels to extinction in much of the UK through a combination of competition and transmission of squirrel pox virus. The impact on the UK forestry industry and conservation efforts is substantial. The annual cost of the damage to forests, and associated control efforts amounts to an estimated £ 40-50 million with at least and a further £ 1 million spent on red squirrel conservation in northern England and Scotland where red squirrels have not yet been driven to extinction. To date, there has been no successful method developed for the long-term control (nor indeed eradication) of grey squirrel populations. Hitherto, prevention of damage to trees has relied largely on the use of warfarin, however approval for the use of warfarin as a plant protection product will be withdrawn in September 2015. The large and growing economic damage to commercial deciduous forestry has major long term implications for the makeup of the UK's landscape and rural economic activity. As a result of the combination of threats posed by grey squirrels, Chalara on ash and climate change, woodland owners (including CONFOR members, project partner #1) are now questioning the viability of attempting to grow any of the principle hardwood species in Britain. The loss of red squirrels from most of England deprives much of the UK public from experiencing the interactions with a species with which they have strong cultural ties. Indeed, with the exception of a few, small, intensively managed red squirrel populations the red squirrel is now almost entirely absent from England and Wales. Its future relies on ongoing expenditure by the public purse and the activities of committed NGOs (in particular RSNE, project partner #2). A major concern is that the progress in red squirrel conservation achieved by the trapping and shooting of grey squirrels to date will be lost, if funding to maintain grey squirrel control cannot be sustained.The recent discovery by Dr Sheehy that the recovery and spread of the native pine marten in Ireland has led to a major decline in grey, but not red, squirrels offers both hope of a solution and an exceptional cross-disciplinary training opportunity for a PhD student to tackle fundamental ecological issues with profound relevance to the forestry industry, rural economy and conservation. The pine marten population was practically extinct, the Scottish population have recovered spectacularly in recent years, and are now just miles away from the English border, meaning natural recolonisation of England from the north is imminent. Conservation efforts in Wales are also underway by the VWT (project partner #3). The recovery and spread of the pine marten on mainland Britain offers unprecedented hope of a solution to the problems caused by grey squirrels. However, the recovery of a carnivore population will inevitably present challenges, especially when a species returns after an absence of many years. Land managers have become accustomed over generations to living in a predator-poor environment, in which certain practices can be easily maintained because predators are scarce, absent or can be legally controlled. Similarly, wild prey populations can become 'predator-naive', developing patterns of behaviour and reproductive output that are unsustainable in the presence of their natural predators. In this context, as pine martens are encouraged to recover, a period of adjustment will be required during which both human and wildlife populations adapt to a more natural environment. Inevitably conflicts will arise where the recovery of the predator population causes or threatens to cause loss to other stakeholders, or requires land-managers to undergo change in practices.