“貍”是一個萌萌噠漢字，觀之則有花斑狀霜浴、毛絨絨之感晶衷。古人戲?qū)⒓邑埛Q之為“貍奴”。陸務(wù)觀在《十一月四日風(fēng)雨大作》中曾有溫暖的兩句：溪柴火暖面粘軟，我與貍奴不出門晌纫。陸游一生為情所困税迷，與表妹唐琬的愛情頗多曲折、不得相守锹漱，報國又有“胡未滅箭养，鬢先秋，淚空流”的蒼涼哥牍，所幸晚年得此貍奴相伴毕泌。貍奴又向花間戲晚晴的畫面，也許千年前就給大文豪帶去了些許的慰藉嗅辣。腦補陸鏟屎官拿著小魚口呼“阿貍”撼泛，頓使愛國詩人的形象多了幾分溫暖和親切，也使得“貍”字觀之可親澡谭。
“貍”在中文中泛指長脊類哺乳動物愿题，善伏之獸。毛皮珍貴蛙奖，因此“貍裘”價值斐然潘酗。大概古人把毛絨絨的萌物統(tǒng)稱為“貍”。今天要說的“河貍”外永，就是極具代表性的小可愛一枚崎脉。
河貍是美洲土著的嚙齒類動物，以樹根伯顶、樹皮為食囚灼，擅長游泳和潛水。不知道為什么兒童文學(xué)和影視偏愛嚙齒類的老鼠祭衩，米老鼠灶体、貓和老鼠、舒克和貝塔都以老鼠為原型掐暮，而老鼠的遠(yuǎn)房表哥河貍卻無人問津蝎抽。事實上河貍表哥不容小覷。首先呢路克，他是顧家的暖男一枚樟结。河貍愛情忠貞，一生只愛一個人精算。成家以后瓢宦，就過著你負(fù)責(zé)帶娃我負(fù)責(zé)看家的歲月靜好的日子。其次灰羽，河貍是陽光向上的事業(yè)型少年驮履。河貍擅長筑壩鱼辙。他們用無堅不摧的牙齒咬斷樹木，然后將樹枝一根一根立于水中玫镐，再用柳條倒戏、樹葉、泥巴穿插于樹枝之間恐似，建成堤壩杜跷，提高局部水位，使得他們的洞穴處于“半水下”的狀態(tài)蹂喻。每個上門提親的河貍小哥都有兩層洋樓：下層是豪華水下河景房葱椭，冬暖夏涼；上層高出水面口四，從此夏天的晚上露天看星星看月亮從詩詞歌賦談到人生哲學(xué)不是夢孵运。小哥可不是隨隨便便的泥瓦工人，那是真正的資深土木工程師蔓彩，在加拿大建成的河貍水壩是美國最大水壩的兩倍之大治笨，在太空上依稀可見。這樣的河貍小哥赤嚼，難怪是麻省理工和加州理工的吉祥物旷赖，實是可遇不可求的人才。
本來有趣的靈魂已經(jīng)萬里挑一了更卒，河貍小哥卻連好看的皮囊也不放過等孵。河貍的裘毛暖和又防水，是冬天保暖炫富的必備品之一蹂空。不過也是因為這一身光鮮亮麗的皮毛俯萌，使得美洲河貍遭受了滅頂之災(zāi)。實是匹夫無罪上枕，懷璧其罪咐熙。1929年，北加州克拉馬斯山谷中最后一只河貍也被捕殺了辨萍。
隨著河貍的消失棋恼，加州和與之比鄰的俄勒岡州的水流和湖泊也發(fā)生了顯著的變化。因著河貍水壩的減少锈玉，水流速度增加爪飘，河床被水流侵蝕越餡越低。水勢難以漫過河堤拉背，河畔的土地便逐漸的枯竭悦施，不久便呈干旱燥裂的狀態(tài)。曾經(jīng)被河貍水壩圍起來的平靜的河水是魚兒棲息繁衍的圣地去团，也是水鳥恬然忘機之所。失去了河貍，魚鳥都無家可歸土陪。
生態(tài)系統(tǒng)的破壞和重建是一個漫長的過程昼汗。人們終于認(rèn)識到河貍筑壩的重要性。然而河貍已經(jīng)沒有了鬼雀，人類只能自己動手顷窒。可是人工的堤壩與河貍的壩相比源哩，笨拙又不易拆除鞋吉，導(dǎo)致大量淤泥和有害物質(zhì)堆積，應(yīng)變性很低励烦，成本卻很高谓着。生態(tài)學(xué)者們開始另想辦法，把河貍“請”回來坛掠。他們自己動手在河堤上建筑河貍水壩的類似物（beaver dam analogs "BDA"), 像河貍一樣使用樹枝和柳條赊锚，然后放三兩只河貍在附近。
善良的河貍不計前嫌屉栓，看到建了一半的堤壩舷蒲，欣然接過善后工作，再次勤勞地日落而作友多，日出而息牲平，為生態(tài)系統(tǒng)的改善鞠躬盡瘁。在BDA和河貍的共同合作下域滥，水流速度減緩纵柿，泥沙下降，河床上升骗绕。繞過堤壩的水沖擊河岸藐窄、拓展河寬，形成了支流和池塘酬土。青樹翠蔓荆忍，蒙絡(luò)搖綴，參差披拂撤缴。
河貍的積極參與使得生態(tài)環(huán)境迅速改善涝缝。BDA建成后1-3年，水流覆蓋面積增加了3倍以上譬重，支流增加1200%拒逮，魚類增加52%。溫暖的河貍用勤勞的雙手筑起自己的生活和家園臀规，與此同時滩援，也造福了周邊的植被和魚蝦。
衣沾不足惜以现，但使愿無違狠怨。
不過雖然益處多多，河貍的回歸也并不完全是一帆風(fēng)順的邑遏。人們早已在曾經(jīng)被支流覆蓋的土地上架橋鋪路佣赖。如今河貍歸來，時而被淹沒的公路令人頭痛记盒。人類曾經(jīng)長驅(qū)直入憎蛤，捕殺河貍以做裘帽，如今它們再次登臺纪吮，人們也還是只從自己的利益角度出發(fā)和思考俩檬。世間安得雙全法呵。生態(tài)和經(jīng)濟是一場有舍有得的博弈碾盟。河貍只是管中窺豹棚辽，可見一斑。第六大生物滅絕正在發(fā)生冰肴，亡羊而補牢屈藐，但求未為晚也。
悟以往之不諫熙尉，知來者之可追联逻。實迷途其未遠(yuǎn)，覺今是而昨非检痰。
Compared to their distant rodent cousins mice, beavers seem to be extremely under-represented in literature and on the screen. Sure, they sometimes appear as supporting actors, like (the "thoughtfully"-named) beaver Mr. Busy in Lady and the Tramp, who helped to bring about the famous spaghetti smooching scene by biting off Lady’s muzzle. Redwall, a fantasy land dedicated to valiant warrior rodents, features only one unnamed beaver. Disney's Zootopia merely pans the camera past a row of beaver construction workers. This scarcity of attention seems extremely unfair in light of the fact that beavers are such amazing animals made for tales and for the screen: extremely fluffy, highly industrious, heart-warmingly family-oriented. Surely they deserve dedicated screen time in their own right.
Beavers are natives of North America. In 1836, when Stephen Meek wandered through the Klamath Mountains, he named what was later known as Scott Valley after one of its most abundant inhabitants - beavers. Beaver Valley was an especially apt name, as it not only described the valley’s inhabitants, it also saluted the valley’s architects. Beavers are nature's very own civil engineers. They use their powerful front teeth to gnaw through trees, dragging logs into river beds, which they then set in upright positions. Next they weave willow branches, leaves and mud in between the logs to create dams. These ingenious dams help to slow water flow, creating a pond haven for beavers to then build their homes - lodges with underwater entry ways. The peaceful ponds the beavers create are also utilized by fish and birds. No other extant animal is known to have more a paw in shaping its landscape than these amazing architects. And beaver dams are no mean feat. The largest known beaver dam is twice the size of the Hoover dam and can be seen from space. It is no wonder then that both MIT and Caltech are proud homes of the Beavers.
However, Stephen didn’t know (or think much about) this when he first encountered beavers in Beaver Valley. What he registered was an abundant source of fine fur and beaver-pelt. As such, beavers were hunted almost to extinction in Northern California and Oregon, setting into action a chain of disastrous events.
Loss of beaver dams resulted in speedier waters, which carved deep into the river beds through erosion. Plains that were usually under water became exposed, dried and barren. Vegetation died. Fish lost their breeding ponds, birds lost quiet resting areas and hunting territories.
The land and its inhabitants pleaded for the return of its furry architect.
Humans tried to fix the problem, to no avail. It turned out that building lodges and dams with manpower is back-breaking (duh) and expensive (huh...). In addition, man-made dams are permanent structures that trap water for far too long, creating excessive sedimentation that spirals down into a muddy mess. So, being the shrewd creatures that we are, humans cast around for cheap labor. Hmmm beavers anyone?
Now this is why beavers deserve to be heroes in tales. Not only are they extremely handsome and talented, they also have shining hearts of gold -? the defining quality of heroes through the ages. When they saw humans building what they called “beaver dam analogs” (BDA) - vertical poles with woven branches, the survivors of the fur trade, along with new beavers reintroduced by tentative humans, didn’t hesitate to lend a paw. Their instincts kicked in and they labored to add more dams while fortifying existing ones.
The results are mind-blowing. The dams diverted streams to cut into banks, widening the channel and decelerating water flow. Sedimentation raised the stream bed, allowing the long awaited-for water to again spread into flood plains and replenish ground water. Irrigation brought back plant life, and fish and birds again thrived in the diverse maze of ponds and streams (see figures above). In some places, within 1-3 years of the introduction of BDAs and beavers, water coverage more than tripled, side streams increased by 1200%, and fish were 52% more likely to survive.
Of course this does not come without skepticism and concerns. What used to be flood plains that welcomed water diverted by beaver dams are now a conglomerate of human civilization: infrastructure that did not like to be underwater, not even occasionally. Hunting beavers had been disastrous for the ecosystem, but reintroducing them into the currently precarious equilibrium could bring just as much harm.
The beavers homeward bound journey is fraught with doubt and uncertainties from the human perspective. We seem to forget that it is in the beavers’ ancestral home that we have set up fort, and refused to share. Even now, we still think of “useful” and “harmful” only in terms to our own species: the maintenance of “our” lands, protection of “our” trees, what we stand to gain and lose economically. And with the threat of the sixth mass extinction hanging over our heads, perhaps even happening as we sit back and contemplate the situation, maybe it is time we gave thought to the wishes and well-beings of others.
Hail the homeward bound beavers.
Reference
Goldfarb, Ben. (2018). Beaver dams without beavers? Artificial logjams are a popular but controversial restoration tool. Science. 10.1126/science.aau3887.
