Northwest's Salmon Population May Be Running Out of Time
A Washington state report put it bluntly ( ): Because of the devastating ( ) effects of climate change and deteriorating ( ) habitats ( ), several species of salmon in the Pacific Northwest are “on the brink of ( ) extinction ( ).”
Of the 14 species of salmon and steelhead trout in Washington state that have been deemed ( ) endangered ( ) and are protected under the Endangered Species Act, 10 are lagging ( ) recovery goals, and five are considered “in crisis,” according to the 2020 State of Salmon in Watersheds report.
“Time is running out,” said the report, which is produced every other year ( ) by the Washington state Recreation and Conservation Office. “The climate is changing, rivers are warming, habitat is diminishing ( ), and the natural systems that support salmon in the Pacific Northwest need help now more than ever.”
Researchers say recovery efforts — involving state and federal agencies, Native American tribes, local conservation groups and others — have helped slow the decline of some salmon populations. The report found that two species — the Hood Canal summer chum and Snake River fall chinook — were approaching ( ) their recovery goals. It also noted that no new salmon species had been added to the endangered list since 2007.
“We are at least treading water,” said Kaleen Cottingham, director of the Washington state Recreation and Conservation Office. “We have not, however, seen the kind of progress ( ) that we had hoped for.”
With the effects of climate change expected to accelerate ( ), researchers said that more must be done to prevent further population decline and the possible extinction of some species.
Salmon play a vital ( ) role in the environment, economy and culture of the Pacific Northwest. At least 138 species depend on salmon for their food in some way. Salmon support an estimated ( ) 16,000 jobs in the fishing industry, and they are a draw ( ) for tourists.
Before the 20th century, an estimated 10 million to 16 million adult salmon and steelhead trout returned annually to the Columbia River system. The current return of wild fish is 2% of that.
One of the largest factors inhibiting salmon recovery is habitat loss. A growing human population has led to development along the shoreline and the addition of bulkheads, or sea walls, that encroach ( ) on beaches where salmon generally find insects and other food. More pavement ( ) and hard surfaces have contributed to an increase in toxic stormwater runoff ( ) that pollutes Puget Sound.
美國西北部鮭魚 陷瀕臨絕種危機
華盛頓州一篇報告直截了當指出，由於氣候變遷跟棲地劣化的毀滅性影響， 美國西北部有數種鮭魚「瀕臨滅絕」。
根據《2020年水域內鮭魚狀況報告》，華盛頓州有14種鮭魚和虹鱒被認定為瀕危物種，並受到《瀕危物種法》保護，其中10種復育進度未能達標，有5種更被認定「處於危機之中」。
這份由華盛頓州休閒與保育辦公室兩年發表一次的報告說：「時間不多了。氣候正在改變，河流水溫正在升高，棲地正在減少，供養美國西北部鮭魚生存的自然系統，如今比以往任何時候都更需要幫助。」
研究人員說，由州與聯邦機構、美國原住民部落、地方保育組織和其他機構共同參與的復育行動，緩和了一些鮭魚數量的減少。報告中發現胡德運河夏天的鉤吻鮭與蛇河秋天的帝王鮭兩種鮭魚，復育正接近目標。報告還指出，自2007年以來沒有新的鮭魚種列入瀕危名單。
華盛頓州休閒與保育辦公室主任Kaleen Cottingham說：「我們至少勉強穩住了情況，但我們沒有看到我們所期望的進展。」
研究人員表示，氣候變遷的影響料將加速，必須更加努力以防止鮭魚數量進一步減少和一些魚種的滅絕。
鮭魚在美國西北部環境、經濟與文化中扮演至關重要角色。在某種程度上，至少有138個物種以鮭魚為食。鮭魚為漁業提供約1萬6千個工作，並吸引大量遊客。
20世紀以前，估計每年有1000萬到1600萬成年鮭魚和虹鱒回到哥倫比亞河水系。目前返回的野生鮭魚數量只有這個數字的2％。
阻礙鮭魚復育的最大原因之一為棲地喪失，不斷成長的人口導致海岸沿線的開發，加上隔板或海堤的增加，這些侵占了鮭魚平常尋找昆蟲及其他食物的海灘。更多的鋪裝路面和堅硬的地面導致有毒雨水流量的增加，進而汙染了普吉特海灣。
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return loss 在 [問題] 量測return loss震盪的原因- 看板comm_and_RF 的推薦與評價
看了一篇paper
這篇paper中的天線量測return loss圖
會有小幅度的起伏震盪
paper中作者有提到
The oscillation of the return loss
probably comes from the dispersion of the substrate
但我不太了解 為何基底的色散會造成return loss的震盪
希望能得到解答 謝謝
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