These are grizzly bears. As you can see, they have big teeth and giant claws.
这些是灰熊。如你所见，它们有巨大的牙齿和下颚。
But once you get to know them better, they're not as ferocious as you might think.
但是如果你进一步地了解它们，它们并没有你想象的那么凶残。
They play a critical role in the function of our ecosystems, but, unfortunately, their habitat is dwindling fast.
它们在我们的生态系统中扮演着重要的角色，然而不幸的是，它们的栖息地正在迅速减少。
In order to protect them, it's important to know why do grizzlies choose certain areas to inhabit in the first place?
为了保护它们，我们必须了解为什么灰熊会选择某些特定的地区作为它们一开始的栖息地呢？
Let's look at a threatened population of bears living in the rocky mountains of Canada.
我们来看看这一群受到威胁的熊，它们生活在加拿大的落基山脉。
Remember those giant claws? Well, they're not for what you might think.
还记得那些巨大的爪子吗？这爪子可能跟你想的不太一样。
They have evolved specifically for digging up energy-rich roots.
它们已经进化为专门用于挖出热量丰富的根茎。
It turns out that grizzlies eat a lot of plants.
原来灰熊会吃大量的植物。
The ones that live here are almost vegetarians.
生活在这里的灰熊几乎都是素食动物。
You see, unlike other predators, grizzlies have diverse diets that can include up to 90% vegetation.
你看，不像其它食肉动物，灰熊有更丰富多样的饮食，其中高达90%都是植物。
However, maintaining a diet of plants can be difficult.
但是保持以植物为食并没有那么容易。
In these northern latitudes, you have distinct seasons
这些北部地区有着分明的四季，
where it's really nice and green for part of the year and really cold for the other part.
一年中有些时候气候会很好，绿意盎然，而其它时候却非常寒冷。
If you eat plants, you have almost nothing to eat for the cold part of the year.
如果你以植物为食，那么在寒冷的季节里，你几乎没什么东西可以吃。
So, you either have to migrate like geese or hibernate like ground squirrels.
所以，你要么像大雁一样迁徙，要么像地松鼠一样冬眠。
Grizzly bears hibernate. Their behaviors are closely synchronized with the seasons.
灰熊会冬眠。它们的行为与季节变化紧密地保持一致。
During the summer, they have to pack on enough body fat to survive the winter.
在夏季，它们必须储存足够的身体脂肪，以度过冬天。
Without it, they would either starve or not have enough energy to successfully produce offspring.
没有这些脂肪，它们要么就挨饿，要么就没有足够的能量来成功繁衍后代。
But when you eat mostly plants, it's hard to gain a lot of weight.
但是当你主要食用植物的时候，想让体重大幅度增加是很难的。
You need to be a highly effective forager.
你需要成为一个高效的采集者。
So, bears tightly follow the schedule of the plants and harvest them like crops at the point in time when they are at the most nutritious.
所以，灰熊们非常严格地遵守着植物的生长周期，像割庄稼一样，在它们最有营养的时候采摘。
This will happen in different places at different times.
这样的收割要在不同的地方和时间进行。

In autumn, a large male grizzly can eat up to 200,000 berries in a single day.
在秋季，一头巨大的雄性灰熊一天可以吃掉高达200000颗浆果。
Therefore, to protect these bears, researchers want to take a closer look at the seasonal interaction
因此，为了保护这些熊，科学家们想更近距离地观察
between grizzlies and plants to identify areas of the highest quality habitat.
灰熊和植物之间季节性的相互影响，以便识别出最优质的栖息地。
This begins 700 kilometers up in space.
它们先从70万米的高空开始。
Up here, two NASA satellites carry sensors that are sensitive to the light reflected by vegetation.
在这里，有两颗NASA卫星携带着感应器，可以检测出植被反射的光线。
Every species of plant reflects a unique combination of wave lengths,
每种植物会反射出一个特殊的波长组合，
called spectral signatures that act like different chords on a piano but use light instead of sound.
这叫做光谱特征，如同钢琴上不同的和弦，但是是用光来代替声音。
These signatures are recorded by the satellites every day and are combined like frames in a movie
卫星每天记录下这些光谱特征，并将它们像电影框架一样合并，
so you can watch the vegetation grow over an entire summer.
这样你就能看到整个夏天里植被的生长。
Simultaneously, the movements of bears wearing GPS collars are monitored
与此同时，熊的移动轨迹由它们携带的GPS项圈来监测，
to see how they respond to the ebb and flow of nutrition throughout their habitat.
以观察它们对于栖息地中食物养分流动和减退的反应。
Now, instead of ordinary, static habitat maps,
现在，普通的静态栖息地图已经被取代，
these dynamic, time-lapse habitat maps could be used for grizzly bear conservation in a number of ways.
而这些动态的、低速度的栖息地图，可以在各个方面用来对灰熊的保护。
First, they help calculate the carrying capacity of the study area.
首先，它们可以帮助计算指定地区的承载能力。
In other words, how many bears can the remaining habitat support? Is there enough food to go around?
也就是说，余下的栖息地可以养活多少头灰熊？这里有足够的食物吗？
Second, the maps show where bears will be foraging at specific times.
第二，这些地图可以显示出在某个时间段中灰熊会在哪里采集食物。
We can prevent disturbing the bears and stressing them out by avoiding these areas during important feeding periods.
我们可以通过避免在重要的进食时间进入这些地区，以免惊扰到这些灰熊、使它们承受重压。
Finally, the maps can be used to predict the effects of climate change,
最后，这些动态地图可以用来预测气候变化的影响，
where shifting annual temperatures will alter the rate of plant growth,
因为每年的温度变化会改变植物的生长速度，
throwing the bears' precise foraging schedule out of whack.
导致灰熊采集食物的精确时间表被严重破坏。
This provides less food and increases competition between bears.
食物的供应减少致使灰熊之间的竞争加剧。
Grizzlies are charismatic symbols of the wilderness.
灰熊是荒野的魅力象征。
These habitat maps made from satellite imagery can not only help conserve grizzly bears but all sorts of different species.
这些由卫星图像制成的栖息地图不仅能够帮助保护灰熊，而且还能保护不同的物种。
They aid us in understanding how ecosystems function, where they are threatened,
这些地图能帮助我们理解生态系统如何运转，它们哪里受到了威胁，
and how we can try to keep our fragile, amazing planet intact.
以及我们要如何努力保护我们脆弱而美好的星球。