有證據顯示衣索比亞的高地曾經主要被森林所覆蓋，而森林的消失是最近的事。衣索比亞的總統吉爾馬．沃爾德．喬治斯在衣國新的永續土地管理平台發表會上說到，在他還是年輕的領航員時曾飛越衣國上空，整個國土幾乎為林地所覆蓋。但令人傷心失望的是，這些林地在過去這段時間不斷地遭到砍伐。林地的砍伐與自然棲息地的消失，是人類為榨取大自然以獲利所做的一連串活動的開始。但人類的榨取過程是傳統的線性模式—搾取，利用，丟棄，再回頭搾取更多。這樣的程序一再反覆進行，而歷史告訴我們，過去曾輝煌一時的許多人類文明最後終究毀滅，原因就在其放任生態系統的瓦解。
在靠近Mekelle的北衣索比亞，我目睹並拍攝下衣索比亞政府、WFP Meret Programme、與德國技術合作公司所合作的集水區生態修復計畫。不同於首都巴哈達的是，這裡的年降雨量只有200-600公釐，而且降雨方式又大又急，無法預測。雖然與塔納湖的1800公釐年降雨量相比之下偏少，但在生態修復工程的保育結果奏效後，雨水得以滲入並蓄積在土壤裡，當地的降雨量其實綽綽有餘。
Mekelle一帶的成果告訴我們，即使在雨量少又不穩定的狀況下，還是可以透過物理和生物方式的介入，來修復集水區的生態系統。在一個子集水區中我遇到一個積極的農夫，他建了許多的介入設施來使雨水得以蓄積。在這些新設施的作用之下雨水得以導入，再加上生物方式的介入，例如植草以在雨季時穩固土壤，在旱季時蓄積土壤的濕度，農民可以輕易地為他們的作物收集到全年所需的水量。透過減緩徑流的速度，每年200-600的降雨量不會像以往一樣全部一瀉千里，而是得以滲入並蓄積於集水區內，使得谷中植物和居民的用水所需得以滿足。結果，修復的速度出奇地快。如此新的集水介入設施與管制放牧的政策雙管齊下，使得下游地區的地下水面在僅僅兩季之內，就上漲了1.5公尺之高。這個山谷在短短幾年內就再度變得綠意盎然，而隨著地下水面的升高，灌溉系統的改善也增加了農民的收成。當這個地區開始使用多層次耕種法種植多年生作物時，不但生產力大增，帶動農民的收入成長，當地的生態系統也可以獲得修復和維護。這意味著至少這個山谷的未來是永續的。而這也是繼中國黃土高原後的成功案例，告訴我們：長時間大規模遭破壞的生態系統是有可能修復的。
在這之中，我們所看到的應用層面是相當深遠的。這樣類型的介入方式需要謹慎研究、全面瞭解，並在全衣索比亞及面臨相同問題的地區大規模地執行。如果正如我們所見的，低降雨量地區的水文功能可以藉由提升地下水而獲得修復，則若是在高雨量地區實行這些措施呢？讓雨水得以滲入並蓄積於土壤中、提升地下水面、修復地表植披以增進土壤的濕度、養分循環、碳截存及生物多樣性。雖然長久以來非洲和貧窮兩字幾乎是劃上等號，但就根本上而言，非洲原本應該會是片富裕的土地。非洲最大的財富來自於水和植披。但矛盾之處仍揮之不散，不是因為我們仍不瞭解就是因為我們還沒有付出行動。
就我的觀察，氣候變遷、生物多樣性的消失、沙漠化問題、乾淨水源的缺乏、以及貧窮等問題都來自相同的根源。如果我們能夠解決生態系統功能的失能，上述的其他問題也可以迎刃而解。而這些全球的生態問題都清楚地顯示：全世界富人的未來與生活在世界邊緣，生態遭破壞地區窮人的未來是緊緊相扣的。因為兩者都取決於同一個條件：具全球規模的良好生態系統功能。如果是這樣，我們該做什麼就很清楚了，同時我們也知道這是可以造福全人類的，因此每一個人都有責任參與。生活在生態系統嚴重破壞地區的窮人可以提供勞力，以修復大面積的土地。而其他的富人則負責提供科學研究、技術、管理以及所需資金。有趣的是，其實這一點也不貴，而且這比我們任由情況繼續下去所需的花費要少多了。
我最近在肯亞認識了René Haller博士。René Haller博士是一位瑞士的農學家，住在非洲已有超過五十年的時間。René在Bamburi水泥公司任職的期間承接了一項任務，就是修復水泥公司的採石場，這個採石場中所有的碳酸鈣沈積物都被挖掘殆盡，只剩光禿禿的岩床和地表下的鹹水。經由研究一種樹種（木麻黃casuarian）和一種節肢動物（epidlous pulchripes）的關係，René發現他能夠藉此在岩床上製造腐殖質。在René Haller的領導之下，他的團隊有了驚人的成果。原來土地裸露的採石場居然變成了一個自然公園，那裡也是我所看過最美麗、生物多樣性最豐富的地方之一。試想如果激勵René Haller博士和其團隊的思考方式及努力，可以用在世界上其他的地方，這個世界會有多麼不一樣。
我們現在知道只要雨水充足、並且有製造生物質量和有機物質的能力，就可以修復大面積的受損生態系統。這結論甚至在低雨量與高鹽分的地方都被證實是可行的。在非洲的許多地方，擁有無窮的修復潛力。這是我們可以截存大量碳的地方，以彌補開發國家所排放的廢氣量。這也是我們可以解決乾淨水源缺發與土地沙漠化問題的所在。當中的難度之高是無庸置疑的。解決貧窮問題與修復生態系統功能的困難度眾所皆知，但我們也知道是可以做到的。
因為我們的瞭解，就成為我們在這個世代的中心使命。我們現在所做的決定和行為都會直接的影響地球未來的面貌。地球在下一代是會成為充滿沙漠的危險禁地，還是生態系統功能健全的綠色星球，都取決於我們的選擇。而這也會決定我們的孩子與他們下一代的生活品質、經濟的永續性、政府的未來，甚至地球所有物種的存亡。
現代的基因研究顯示，所有的人類其實都源自於非洲東部的大裂谷，也就是說，我們都是非洲人。從生態角度來看，我們都是地球人。我們在經濟上的連結是前所未有的緊密，每一個人都是利益關係者。過去長久以來因為我們個人的利益和貪婪在驅動著我們的行為，才造就了貧窮的問題和重大的生態危機。現在我們有充足的理由和可行的方法，讓我們可以重返人類生命的搖籃，解決貧窮問題以及生態系統功能受損的根源。因為我們知道造成功能毀損與重建的方法，因此造就一個失調還是健全的生態系統功能，都取決於我們的選擇。我們的選擇，也是地球的希望。
There is evidence that the Ethiopian highlands were mainly forested and that the destruction of these forests has been relatively recent. The President of Ethiopia, His Excellency Girma Wolde-Giorgis speaking at the Launch of Ethiopia’s new Sustainable Land Management Platform, stated that as a young navigator he flew across an almost fully forested country and has been continuously saddened as the once great forests have been consistently cut down. The cutting of trees and the loss of natural habitats were the beginning of a series of human interventions to extract wealth and benefit from nature. But human extraction has been traditionally a linear system. Extract, use and throw away … only to return to extract some more. This eventually leads to ecosystem collapse, when all the resources have been extracted. This progression has been repeated time and time again. History shows us the ruins of once mighty civilizations that are but memories because they allowed their ecosystems to collapse.
Near Mekelle in Tigray Northern Ethiopia, I was able to see and document the efforts of the Ethiopian Government in collaboration with the WFP Meret Programme and the German Technical Assistance Agency GTZ in restoring ecological function in degraded watersheds. In this region, unlike the Bahir Dar region, there is only between 200 and 600 millimeters of rainfall per year. When the rains do come they can be both heavy and unpredictable. While this seems comparatively low in relation to the 1800 millimeters near Lake Tana, the new restoration and conservation efforts are proving that it can be sufficient, when the principles governing its infiltration and retention are understood.
What the work near Mekelle is showing is that it is possible through physical and biological intervention to restore hydrological function to a watershed even in low and erratic rainfall conditions. In one sub-watershed I visited a motivated farmer had made a very large number of interventions. Dozens of structures have been built for water retention. Directing rainfall through these new structures and combining this with biological inputs such as grasses that stabilize the soil during rainfall and retain soil moisture in the dry season, have made it possible for farmers to easily access water for their crops throughout the year. By slowing the runoff, the 200 to 600 millimeters of rainfall each year do not run off in a flood but are infiltrated and retained within the watershed to serve the needs of the plants and the people in the valley. Recovery has been amazingly fast. The new water harvesting interventions, coupled with a controlled grazing policy, have allowed the water table to rise to within 1.5 meters of the surface in the lower parts of the watershed after only 2 seasons. This one valley has become green again in only a few years and with the water table raised irrigation has increased farmers yield. When perennial crops and multistory cropping are used this region can both massively increase productivity and income for the people and restore and maintain ecosystem function, meaning that at least for this one valley the future is sustainable. This follows findings in China’s Loess Plateau that have shown that it is possible to rehabilitate large-scale damaged ecosystems including returning ecosystem function that has been lost over large areas and long periods of time.
The implications of what we have seen are profound. This type of intervention needs to be studied carefully, fully understood and implemented at scale, everywhere in Ethiopia and everywhere the same problem is faced. If, as it seems, it is possible to restore hydrological function in low rainfall areas by recharging the ground water what would happen if this were done in areas with high rainfall? Infiltrating and retaining rainfall, recharging the ground water, and restoring the vegetation cover causes increases in soil moisture, relative humidity, nutrient cycling, carbon sequestration and biodiversity. Although Africa and poverty have been linked for some time, Africa is fundamentally wealthy. The wealth comes from the water and the vegetation. The paradox remains because we have either not understood this or we have not acted on it.
It seems to me that a strong case can be made that climate change, biodiversity loss, desertification, fresh water stress, poverty and disparity all have the same roots. If we address ecosystem function we will in effect be addressing all of these problems. These global ecological issues also clearly illustrate that the future of the wealthy all over the world and the future of the poor at the edges of large degraded ecosystems will be determined by the same criteria, functional ecosystems on a planetary scale. That being the case, we know what we need to do, we know how to do it, and we know that everyone on Earth will benefit and so has a responsibility to participate. The poor living in degraded ecosystems can provide the labor needed to rehabilitate large areas of land. The wealthy around the world can provide the scientific understanding, the technical capability, the management capacity and the capital needed to restore degraded ecosystems everywhere. Interestingly, it isn’t even expensive and it is certainly less expensive than allowing the situation to continue.
In Kenya, I recently met Dr. René Haller. Dr. Haller is a Swiss agronomist who has lived in Africa for more than 50 years. Working for the Bamburi Cement Co. in Mombassa, René took on the task of rehabilitating the cement quarries after the company had dug out the calcium carbonate deposits, leaving a bare rock floor with saline water just below the surface. By studying the interaction between a tree species (casuarina) and a species of millipedes (epibolus pulchripes) René discovered that he could generate humus on the bedrock. What the teams of people working under René Haller’s direction have achieved is very nearly miraculous. The bare earth of the quarry has been transformed into a nature park that is one of the most beautiful and diverse places I have ever seen. Imagine if the thinking and dedication that has motivated Dr. Haller and his team were applied everywhere.
We now know that as long as there is sufficient rainfall and the ability to generate biomass and necromass, it is possible to restore large-scale damaged ecosystems. This has been shown to be true even in low rainfall and saline conditions. In many parts of Africa, the potential of restoration is enormous. This is where we can sequester vast amounts of carbon to offset the wasteful emissions in the developed world. This is where we can ensure the survival of precious wild genetic material. This is where we can address the issue of fresh water stress and desertification. There is no doubt that the degree of difficulty is high. No one doubts that ending poverty and restoring ecosystem function is very, very hard. But we also that it is possible.
Because we know this it becomes the central responsibility of our time. Our decisions and actions now will literally determine what the Earth will look like in the future. It’s our choice whether the Earth for the next generations is a forbidding and dangerous place with expanding deserts or a fully vegetated planet with functional ecosystems. This will certainly determine the quality of life our children and their children will experience, the sustainability of the economy, the future of our political institutions and perhaps even the survival of the species.
Modern genetics has shown that everyone on earth can trace their ancestry back to a common ancestor in Africa’s Great Rift Valley. So in fact, we are all Africans. From an ecological perspective we are all from the Earth. Economically we are ever more closely interlinked. Everyone has a stake in the outcome. We have a long history of greed and self-interest, motivating our actions and this has caused economic disparity and massive ecological damage. Now we have both a compelling rationale and a functional model for returning to the cradle of humanity to seriously address the fundamental causes of poverty and ecosystem dysfunction? Because we know to a large degree what constitutes functionality and what disrupts it on the Earth, it is our choice to have either functional or dysfunctional ecosystems. It’s our choice and the Earth’s Hope.
關於作者：
John Liu 是一位美國出生的華裔，在中國居住了長達25年。他曾協助建立起哥倫比亞廣播公司（CBS）的北京據點，之後在其新聞部工作超過十年。他也曾經在義大利廣播電視公司（RAI Italian Television）和德國電視二台（Zweites Deutsches Fernsehen）當過攝影師。自1997年以來，John Liu就開始主導 「環境教育媒體宣導計畫」，希望能用電視的影響力在中國還有其他國家來傳達生態系統、永續發展和公共衛生等訊息。
