According to conservationists, populations of around two thirds of butterfly species have declined in Britain over the past 40 years. If this trend continues, it might have unpredictable knock-on effects for other species in the ecosystem. Butterfly eggs develop into caterpillars and these insects, which are the second stage in a new butterfly's lifecycle, consume vast quantities of plant material, and in turn act as prey for birds as well as bats and other small mammals. Only by arming themselves with an understanding of why butterfly numbers are down can conservationists hope to halt or reverse the decline.

据自然资源保护人士称，在过去的40年里，英国大约三分之二的蝴蝶种类的数量已经下降。如果这种趋势继续下去，可能会对生态系统中的其他物种产生不可预测的连锁反应。蝴蝶卵发育成毛毛虫，这些昆虫是新蝴蝶生命周期的第二阶段，它们消耗大量的植物材料，反过来又成为鸟类、蝙蝠和其他小型哺乳动物的猎物。只有了解蝴蝶数量下降的原因，环保主义者才有希望阻止或扭转这种下降。

Butterflies prefer outdoor conditions to be 'just right', which means neither too hot nor too cold. Under the conditions of climate change, the temperature at any given time in summer is generally getting warmer, leaving butterflies with the challenge of how to deal with this. One of the main ways in which species are ensuring conditions suit them is by changing the time of year at which they are active and reproduce. Scientists refer to the timing of such lifecycle events as 'phenology', so when an animal or plant starts to do something earlier in the year than it usually does, it is said to be 'advancing its phenology'.

蝴蝶喜欢“恰到好处”的户外环境，也就是说既不太热也不太冷。在气候变化的条件下，夏季任何时候的温度通常都在变暖，这给蝴蝶带来了如何应对的挑战。物种确保环境适合它们的主要方式之一是改变一年中它们活动和繁殖的时间。科学家们把这种生命周期事件发生的时间称为“物候学”，所以当一种动物或植物在一年中比通常更早开始做某事时，就被称为“物候学提前”。

These advances have been observed already in a wide range of butterflies – indeed, most species are advancing their phenology to some extent. In Britain, as the average spring temperature has increased by roughly 0.5 °C over the past 20 years, species have advanced by between three days and a week on average, to keep in line with cooler temperatures. Is this a sign that butterflies are well equipped to cope with climate change, and readily adjust to new temperatures? Or are these populations under stress, being dragged along unwillingly by unnaturally fast changes? The answer is still unknown, but a new study is seeking to answer these questions.

这些进步已经在很多种类的蝴蝶身上被观察到——事实上，大多数种类的蝴蝶都在一定程度上推进了它们的物候学。在英国，在过去的20年里，春季的平均气温上升了大约0.5°C，为了适应较低的温度，物种平均提前了三天到一周。这是否表明蝴蝶已经做好了应对气候变化的准备，并能迅速适应新的温度?或者这些种群正处于压力之下，被不自然的快速变化不情愿地拖着走?答案仍然未知，但一项新的研究正在试图回答这些问题。

First, the researchers pulled together data from millions of records that had been submitted by butterfly enthusiasts – people who spend their free time observing the activities of different species. This provided information on 130 species of butterflies in Great Britain every year for a 20-year period. They then estimated the abundance and distribution of each species across this time, along with how far north in the country they had moved. The data also, crucially, allowed researchers to estimate subtle changes in what time of the year each species was changing into an adult butterfly.

首先，研究人员从蝴蝶爱好者提交的数百万份记录中收集了数据，这些爱好者利用业余时间观察不同物种的活动。在20年的时间里，每年都会提供英国130种蝴蝶的信息。然后，他们估计了这段时间内每种物种的丰度和分布，以及它们向北移动了多远。至关重要的是，这些数据还使研究人员能够估计出每种蝴蝶在一年中什么时候变成成年蝴蝶的细微变化。

Analysing the trends in each variable, the researchers discovered that species with more flexible lifecycles were more likely to be able to benefit from an earlier emergence driven by climate change. Some species are able to go from caterpillar to butterfly twice or more per year, so that the individual butterflies you see flying in the spring are the grandchildren or great-grandchildren of the individuals seen a year previously.

研究人员分析了每个变量的趋势，发现生命周期更灵活的物种更有可能从气候变化推动的早期出现中受益。有些种类每年能从毛毛虫变成蝴蝶两次或更多，所以你在春天看到的蝴蝶是一年前看到的蝴蝶的孙子或曾孙。

Among these species, researchers observed that those which have been advancing their phenology the most over the 20-year study period also had the most positive trends in abundance, distribution and northwards extent. For these species, such as Britain's tiniest butterfly, the dainty Small Blue, whose colonies are up to a hundred strong, some develop into butterflies early in spring, allowing their summer generations to complete another reproductive cycle by autumn so that more population growth occurs.

在这些物种中，物候变化最快的物种在丰度、分布和向北扩展方面也有最积极的趋势。对于这些物种来说，比如英国最小的蝴蝶，精致的小蓝蝴蝶，它的种群多达100只，一些在早春就发育成蝴蝶，让它们的夏季后代在秋天完成另一个繁殖周期，这样就会出现更多的种群增长。

Other species, however, are less flexible and restricted to a single reproductive cycle per year. For these species, there was no evidence of any benefit to emerging earlier. Indeed, worryingly, it was found that the species in this group that specialise in very specific habitat types, often related to the caterpillar's preferred diet, actually tended to be most at harm from advancing phenology. The beautiful High Brown Fritillary, often described as Britain's most endangered butterfly, is in this group. It is found only in coppiced woodland and limestone pavement habitats. It is also a single-generation butterfly that has advanced its phenology. This suggests that climate change, while undoubtedly not the sole cause, might have played a part in the downfall of this species.

然而，其他物种的灵活性较差，每年仅限于一次繁殖周期。对于这些物种来说，没有证据表明更早出现有任何好处。事实上，令人担忧的是，研究发现，这一组中专门从事非常特定的栖息地类型的物种，通常与毛虫的偏好饮食有关，实际上往往最容易受到物候变化的伤害。美丽的高褐贝母，通常被描述为英国最濒危的蝴蝶，就在这个群体中。它只存在于覆盖的林地和石灰岩路面栖息地。它也是一种单代蝴蝶，它的物候学已经提前了。这表明，虽然气候变化无疑不是唯一的原因，但它可能在这个物种的灭绝中起了一定作用。

All is not lost, however. Many of Britain's single-generation species show the capacity, in continental Europe, to add a second generation in years that are sufficiently warm. Therefore, as the climate continues to warm, species like the Silver-studded Blue might be able to switch to multiple generations in the UK as well, and so begin to extract benefits from the additional warmth, potentially leading to population increases.

然而，并不是所有的事情都失败了。在欧洲大陆，许多英国单代物种显示出在足够温暖的年份增加第二代的能力。因此，随着气候持续变暖，像银刺蓝这样的物种也可能在英国切换到多代，从而开始从额外的温暖中获益，从而潜在地导致人口增长。

More immediately, conservationists can arm themselves with all this knowledge to spot the warning signs of species that may be at risk. The White Admiral of southern England, a much sought-after butterfly, experienced a significant increase in numbers from the 1920s but has shown a considerable decline in the past 20 years. This may be because the caterpillar exists solely on a diet of a plant called honeysuckle. But it is also likely to be due to climate change.

更直接的是，环保主义者可以用所有这些知识武装自己，以发现可能处于危险中的物种的警告信号。英国南部的白色海军上将是一种非常受欢迎的蝴蝶，从20世纪20年代开始，它的数量显著增加，但在过去的20年里却出现了相当大的下降。这可能是因为毛毛虫只以一种叫做金银花的植物为食。但也有可能是气候变化造成的。