As you can see, they have big teeth and giant claws.

如你所見， 牠們有巨大的牙齒和爪子。

But once you get to know them better,

不過如果你更了解牠們一點，

they're not as ferocious as you might think.

牠們並不像你想像中那樣兇猛。

They play a critical role in the function of our ecosystems,

牠們在我們的生態系裡 扮演了關鍵的角色，

but, unfortunately, their habitat is dwindling fast.

但不幸地，牠們的棲地正不斷在減少。

In order to protect them,

為了保護牠們，

it's important to know

我們必須瞭解

why do grizzlies choose certain areas

為什麼灰熊會選擇

to inhabit in the first place?

居住在某些特別地方？

Let's look at a threatened population of bears

我們來看看 生活在加拿大洛磯山脈

living in the rocky mountains of Canada.

那些瀕臨絕種的灰熊。

Remember those giant claws?

還記得牠們的大爪嗎？

Well, they're not for what you might think.

嗯，那些大爪可能跟你想得不太一樣。

They have evolved specifically

牠們是特別演化來

for digging up energy-rich roots.

挖掘營養豐富的根莖類的。

It turns out that grizzlies eat a lot of plants.

其實灰熊攝取大量的植物。

The ones that live here are almost vegetarians.

你看到的這隻幾乎是吃素的。

You see, unlike other predators,

跟別的掠食者不一樣，

grizzlies have diverse diets

灰熊吃的東西範圍很廣，

that can include up to 90% vegetation.

其中可能有九成是蔬果。

However, maintaining a diet of plants can be difficult.

然而，要靠植物過生活沒那麼簡單。

In these northern latitudes, you have distinct seasons

在這些高緯地區四季分明：

where it's really nice and green for part of the year

一年之中 有時候既舒爽又富綠意、

and really cold for the other part.

而有時候又非常冷。

If you eat plants, you have almost nothing to eat

如果你靠植物維生， 在寒冷的季節

for the cold part of the year.

你幾乎沒東西吃。

So, you either have to migrate like geese

所以，或者你必須像野雁那樣遷徒、

or hibernate like ground squirrels.

不然就必須像松鼠那樣冬眠。

Grizzly bears hibernate.

灰熊選擇冬眠。

Their behaviors are closely synchronized with the seasons.

牠們的作息和季節關係非常密切。

During the summer, they have to pack on

夏天的時候，

enough body fat to survive the winter.

牠們會貯存足夠的體脂肪過冬。

Without it, they would either starve

不這麼做，牠們可能就會挨餓、

or not have enough energy

或是沒有足夠的能量

to successfully produce offspring.

來繁衍後代。

But when you eat mostly plants,

但當你主要靠植物維生的時候，

it's hard to gain a lot of weight.

增胖變得很困難。

You need to be a highly effective forager.

你必須是很有效率的覓食者。

So, bears tightly follow the schedule of the plants

所以，灰熊會緊跟著 植物生長的腳步，

and harvest them like crops

並像收割稻穗那樣

at the point in time when they are at the most nutritious.

──在它們養份最多的時候採收下來。

This will happen in different places at different times.

不同地區成熟的時間不一樣。

In autumn, a large male grizzly can eat

在秋天，一隻大型的雄灰熊

up to 200,000 berries in a single day.

一天可以吃掉將近二十萬顆野莓。

Therefore, to protect these bears,

因此，要保護這些灰熊，

researchers want to take a closer look

研究學者會想要更了解

at the seasonal interaction between grizzlies and plants

灰熊和植物之間 隨著季節變化的關係，

to identify areas of the highest quality habitat.

這樣才能找出最佳的棲地。

This begins 700 kilometers up in space.

這計劃在七百公里高的太空中展開。

Up here, two NASA satellites carry sensors

在這裡，有兩顆 NASA 衛星 配備著感應器，

that are sensitive to the light reflected by vegetation.

它們可以感應 植物反射出來的光波。

Every species of plant reflects

每種植物會反射出

a unique combination of wave lengths,

獨特的波長組合，

called spectral signatures

這組合被叫作 「光譜特徵」（spectral signature）。

that act like different chords on a piano

光譜特徵就像是 不同的鋼琴和弦，

but use light instead of sound.

只是現在是光波不是聲波。

These signatures are recorded by the satellites every day

這些特徵 會被衛星一天一天記錄下來，

and are combined like frames in a movie

並像電影分鏡那樣合在一起。

so you can watch the vegetation grow

如此一來你就可以看到

over an entire summer.

整個夏天植物生長的變化。

Simultaneously, the movements of bears

同時，有些灰熊會戴著 GPS 項圈，

wearing GPS collars are monitored

我們就可以追踪牠們的遷徒

to see how they respond to the ebb and flow

來看看牠們如何應對

of nutrition throughout their habitat.

棲地中營養食物的興衰波動。

Now, instead of ordinary, static habitat maps,

相較於傳統、靜態的棲地地圖，

these dynamic, time-lapse habitat maps

這些動態、縮時攝影的棲地地圖

could be used for grizzly bear conservation

可以被廣泛地

in a number of ways.

用在灰熊保育上。

First, they help calculate the carrying capacity

第一，這地圖可以協助估算

of the study area.

研究地區的「環境承載力」。

In other words, how many bears

也就是說，這棲地

can the remaining habitat support?

足以供給多少灰熊在此生活？

Is there enough food to go around?

附近有足夠的食物嗎？

Second, the maps show

第二，這地圖顯現出

where bears will be foraging at specific times.

灰熊在特定時間覓食的地點。

We can prevent disturbing the bears

在重要覓食季節

and stressing them out

避開這些地區，

by avoiding these areas during important feeding periods.

就可以避免打擾或是嚇跑牠們。

Finally, the maps can be used

最後，這地圖也可以用來

to predict the effects of climate change,

預測氣候變遷的影響，

where shifting annual temperatures

隨著年均溫的改變

will alter the rate of plant growth,

植物的生長率也跟著受影響，

throwing the bears' precise foraging schedule out of whack.

這讓灰熊高效率的覓食行程 無法正常進行。

This provides less food

這造成食物變少、

and increases competition between bears.

並增加灰熊之間的競爭。

Grizzlies are charismatic symbols of the wilderness.

灰熊是野外生態的魅力象徵。

These habitat maps made from satellite imagery

這些藉由衛星影像所呈現的棲地地圖

can not only help conserve grizzly bears

不只有助於灰熊保育，

but all sorts of different species.

也適用於不同物種。

They aid us in understanding

地圖幫助我們了解

how ecosystems function,

生態系的運作：

where they are threatened,

牠們如何受到威脅

and how we can try to keep our fragile,

我們又該如何保護這個

amazing planet in tact.

奇妙卻脆弱的星球的完整性呢。