分類: 環保清潔

環境資訊中心外電；姜唯 翻譯；林大利 審校；稿源：ENS

2018年全球碳排創下新高，光是美國就增加了3.4%，海洋跟森林吸碳量都接近上限。哥倫比亞大學學者的最新研究結果再次確認，緩解氣候變遷刻不容緩——極端氣候可能影響陸地吸碳的能力，氣候潮溼年份的吸碳量無法補回乾旱年份減少的吸碳量。

極端氣候可能影響陸地吸碳的能力。圖片來源：Blanscape/Shutterstock.com

人為排放溫室氣體二氧化碳，導致地球大氣中二氧化碳濃度升高，氣候系統被人類活動改變。海洋、森林和草原會吸收部分人類排放的二氧化碳，目前吸收比例大約是50%，反映在珊瑚白化、海洋酸化以及森林儲碳增加等現象。

「不過，我們並不清楚陸地是否能繼續照這個比例吸收人為碳排。一旦陸地達到吸收上限，全球暖化會加速，對人類和環境造成嚴重後果。這表示我們真的必須立刻行動，避免氣候變遷繼續惡化。」主持研究的哥倫比亞環境工程系副教授、地球學院兼任教授根廷（Pierre Gentine）表示。

根廷和他的博士生格林（Julia Green）合作，探討氣候乾濕循環和長期乾旱趨勢如何影響陸地吸收二氧化碳。他們也認為，降雨規律將會改變，影響地球植被吸碳的能力。

為了定義植物和土壤的吸碳量，根廷和格林用政府間氣候變遷專門委員會（IPCC）所定義的「淨生物區系生產力」（net biome productivity，NBP）來計算，也就是一個地區的淨碳增加或減少，等於生態系產碳減去森林大火或砍伐等活動造成的碳損失。

研究團隊用「全球陸地大氣耦合實驗－耦合模型比對計畫」（Global Land Atmosphere Coupling Experiment – Coupled Model Intercomparison Project，GLACE-CMIP5）的四個地球系統模型跑一系列的實驗，隔離出土壤濕度改變所導致的NBP減少，分析出長期土壤濕度趨勢改變對土壤吸碳能力的影響。

「我們發現NBP的值，也就是地表的淨碳增加，在土壤濕度沒有變異時是有變異時的兩倍。」格林說，「如果土壤濕度持續照目前速度減少NBP，陸地吸碳量到本世紀中繼續減少——如模型所顯示——我們很可能會經歷大氣中二氧化碳濃度大幅增加，以及相對應的暖化和氣候變遷。」

根廷和格林的研究結果顯示，土壤濕度變異和變乾都會減少碳匯。

「簡言之，如果接下來100年沒有乾旱跟熱浪，也沒有長期乾旱，陸地吸碳的能力會是現在的兩倍。因為土壤濕度對碳循環非常重要，跟陸地吸碳能力高度相關。」根廷說。

關於植物如何因應水壓力還有許多不確定性，根廷和格林將繼續探討如何量化研究土壤濕度改變對植物的影響。

他們的研究範圍目前聚焦於熱帶地區，因為變數最多、碳匯最高，探討植物活動如何因土壤濕度改變和大氣乾燥程度而改變。

Climate Tipping Point Could Occur Sooner Than We Think NEW YORK, New York, January 23, 2019 (ENS)

A Columbia Engineering study, published today in the journal “Nature,” confirms the urgency of tackling climate change. Global carbon emissions reached a record high in 2018, rising by 3.4 percent in the United States alone, and oceans and forests are approaching their uptake limits.

This demonstrates that wetter-than-normal years do not compensate for losses in carbon uptake during dryer-than-normal years, caused by events such as droughts or heatwaves.

Emissions of the greenhouse gas carbon dioxide, CO2, caused by human activities are increasing the concentration of CO2 in the Earth’s atmosphere and producing unnatural changes to the planet’s climate system. The effects of these emissions on global warming are only partially abated as the land and ocean absorb some of the CO2 emitted by humans burning fossil fuels.

Currently, the oceans and forests and savannas on land are absorbing about 50 percent of these releases, explaining the bleaching of coral reefs and acidification of the ocean, as well as the increase of carbon uptake by forests.

“It is unclear, however, whether the land can continue to uptake anthropogenic emissions at the current rates,” says Pierre Gentine, associate professor of earth and environmental engineering and affiliated with the Earth Institute, who led the study.

“Should the land reach a maximum carbon uptake rate, global warming could accelerate, with important consequences for people and the environment. This means that we all really need to act now to avoid greater consequences of climate change,” Gentine said.

Working with his PhD student Julia Green, Gentine wanted to understand how variability in the hydrological cycle – droughts and floods, and long-term drying trends – was affecting the capacity of the continents to trap some of the emissions of CO2.

They also predict that there will also be a change in rainfall patterns that will likely affect the ability of the Earth’s vegetation to take up carbon.

To define the amount of carbon stored in vegetation and soil, Gentine and Green analyzed net biome productivity, or NBP, defined by the Intergovernmental Panel on Climate Change as the net gain or loss of carbon from a region, equal to the net ecosystem production minus the carbon lost from disturbance like a forest fire or a forest harvest.

The researchers used data from four Earth System Models from the Global Land Atmosphere Coupling Experiment – Coupled Model Intercomparison Project (GLACE-CMIP5), to run a series of experiments to isolate reductions in NBP that are due strictly to changes in soil moisture.

They were able to isolate the effects of changes in long-term soil moisture trends, such as drying, as well as short-term variability, such as the effects of extreme events such as floods and droughts, on the ability of the land to take up carbon.

“We saw that the value of NBP, in this instance a net gain of carbon on the land surface, would actually be almost twice as high if it weren’t for these changes – variability and trend – in soil moisture,” says Green, the paper’s lead author.

“This is a big deal! exclaimed Green. “If soil moisture continues to reduce NBP at the current rate, and the rate of carbon uptake by the land starts to decrease by the middle of this century – as we found in the models – we could potentially see a large increase in the concentration of atmospheric CO2 and a corresponding rise in the effects of global warming and climate change.”

Gentine and Green note that soil-moisture variability reduces the present land carbon sink, and their results show that both variability and drying trends reduce it in the future.

“Essentially, if there were no droughts and heat waves, if there were not going to be any long-term drying over the next century, then the continents would be able to store almost twice as much carbon as they do now,” said Gentine.

“Because soil moisture plays such a large role in the carbon cycle, in the ability of the land to uptake carbon, ” he urged.

There is still a great deal of uncertainty on how plants respond to water stress, and so Green and Gentine will continue their work on improving representations of vegetation response to soil moisture changes.

They are now focusing on the tropics, a region with lots of unknowns, and the largest terrestrial carbon sink, to determine how vegetation activity is being controlled by both changes in soil moisture as well as atmospheric dryness.

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環境資訊中心外電；姜唯 翻譯；林大利 審校；稿源：ENS

一年前，中國宣布不再接受來自國外的回收材料，全世界失去了收購回收紙和塑膠的最大客戶。不過，這個變化也創造出一個買方市場——現在接收回收材料的造紙廠和製造商紛紛要求回收材料中幾乎不能含有任何雜質。有些城市表示無法達到新標準，逐步減少或暫停回收工作，其他如舊金山市則迎接挑戰，重新投入回收業，喊出「一起努力，我們可以。」（Together we can.）

鳥瞰舊金山資源回收公司 Recology 的處理中心。圖片來源：Derrick Coetzee／維基百科

舊金山的資源回收公司「Recology」為其過去一年來的成就感到自豪。2018年，Recology完成了以下行動：

1、加強與國內外回收材料買家的關係，開拓新市場。

2、斥資1400萬美元，重整舊金山96號碼頭上佔地20萬平方英尺的物料回收設施「Recycle Central」，加裝300萬美元的雨水回收系統，還裝了七台高速電腦控制的光學分揀機。

3、建造了一座先進的有機物轉運站，以擴大舊金山領先業界的路邊堆肥收集計畫。

4、向全市的住宅物業提供超過10萬個加大的回收車和縮小的不可回收車。這項措施特別成功。新的加大回收車和縮小的不可回收車鼓勵居民們回收。Recology還更新了垃圾車蓋子上的貼紙，用圖片說明什麼丟在哪裡，並將貼紙應用在該市的31萬3000個回收車和回收桶。

「繼2000年 Fantastic 3 計畫後，就屬這個計畫在減少垃圾掩埋噸位、增加回收和堆肥量上的效果最好，」Recology說。

這些措施讓Recology改善垃圾分類並減少污染，獲得更高品質的回收物資，進而使舊金山更能銷售這些回收物資，為該市的路邊收集計畫提供資金。

Recology的資源回收車。圖片來源：Dllu／維基百科（CC BY-SA 4.0）

路邊堆肥收集不但節省垃圾填埋空間，提供當地農場肥料，減少溫室氣體排放，創造的工作機會比垃圾掩埋場多三倍。

舊金山剛剛達到了堆肥200萬噸有機材料的里程碑，並於12月19日慶祝轉運站擴建部分啟用。這筆1900萬美元的投資增加了舊金山堆肥和庭院修整廢料的收集量，從每天750噸增加到1000多噸。

Recology 2018年完成的其他工作包括安裝全舊金山最大的私有太陽能電池陣列，幫助舊金山達成2030年100％再生能源的目標。此外還有一座新的水回收系統，可減少洗車用水80％，每月可節省數千加侖的飲用水。

San Francisco Doubles Down on Recycling SAN FRANCISCO, California, January 24, 2019 (ENS)

When faced with a challenge, the city of San Francisco rededicated itself to recycling. One year ago, when China announced it would no longer accept shipments of recycled materials from foreign countries, the world lost its biggest customer for bales of recycled paper and recycled plastic.

This created a buyer’s market, and paper mills and manufacturers receiving recycled materials now demand bales that contain almost no impurities.

In response, some cities said they could not meet the new standard and reduced or suspended recycling efforts. By contrast, San Francisco is rising to the challenge and says, “Together we can.”

Recology, San Francisco’s resource recovery company, is taking special pride in its accomplishments to bring better recycling to the City by the Bay. Recology completed the following actions in 2018:

• Strengthened relationships with domestic and foreign buyers of recycled materials and developed new markets.

• Retooled Recycle Central, a 200,000-square-foot Material Recovery Facility on San Francisco’s Pier 96, including installation of a $3 million storm water reclamation system. After the $14 million upgrade, the recycling facility now houses seven high-speed, computer-controlled optical sorters.

• Constructed a state-of-the art organics transfer station to expand San Francisco’s industry-leading curbside composting collection program.

• Delivered more than 100,000 larger recycling and smaller landfill carts to residential properties across the City. This Recology program has been especially successful. New larger recycling bins and smaller refuse bins for residences have encouraged recycling. Recology updated its lid stickers, which use pictures to show what goes where, and applied the stickers to 313,000 carts and containers in San Francisco.

“This program has resulted in the largest decrease of landfill tonnage and increase in recycling and composting since the inception of the Fantastic 3 program in 2000,” Recology says.

These initiatives allow Recology to better sort materials and reduce contamination, resulting in higher-quality bales of finished recycling. Producing high-quality, bales enables San Francisco to market its recycled materials, which helps fund the city’s curbside collection program.

Curbside composting collection saves landfill space, sends nutrients to local farms, reduces greenhouse gas emissions, and creates three times more jobs than landfilling.

San Francisco has just hit the milestone of composting two million tons of organic materials, and on December 19 the city celebrated the opening of the West Wing, an extension of the Transfer Station. The $19 million investment gives San Francisco the capacity to increase the amount of food scraps and yard trimmings collected and transferred to composting facilities from 750 tons to more than 1,000 tons per day.

Other facility improvements completed in 2018 include installing the largest privately owned solar array in San Francisco, supporting the city’s goal of reaching 100 percent renewable energy by 2030.

Recology also installed a new water reclamation system that reduces water used for truck washing by 80 percent, saving thousands of gallons a month of drinking water.

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如果有一件事是重要的，如果能為孩子實現一個願望，那就是人類與大自然和諧共存。

於特有生物研究保育中心服務，小鳥和棲地是主要的研究對象。是龜毛的讀者，認為龜毛是探索世界的美德。

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