Migration

Is Climate Change Forcing Species Migration and Extinction?

Why is it news that various plants and animals are being forced out of their natural habitat because climate is changing? As demonstrated by Figure 1, climate is changing. It would be newsworthy if plants and animals weren’t reacting to changes in their environment. It would mean everything scientists have learned about biologic adaptation is wrong. It would mean that instead of changing behavior in response to environmental changes, life on earth is inflexible.

One recent example of false claims (presented to viewers of FOX cable news) is that the warming of north Atlantic waters is responsible for the appearance of a Great White Shark off the coast of Alaska. The truth is that Great Whites (Carcharadon carcharias) are endothermic – able to elevate their body temperature above that of the surrounding water. They can tolerate a broad temperature range, providing them access to prey (primarily coastal pinnipeds) over a wide ecological niche -- including sub-artic Alaskan waters. They have long been observed along the U.S. coastline from California to Alaska (Figure 9).

As for earth’s plant life, atmospheric CO2 enrichment tends to ease the potentially negative effects of rising temperatures. Studies indicate that more CO2 in the air enables plants to grow better at nearly all temperatures, but especially at higher temperatures. Elevated CO2 boosts the optimum temperature at which plants grow best and it raises the upper-limiting temperature above which plants die. Elevated CO2 makes them much more resistant to heat stress.

It appears that if the atmosphere’s temperature and CO2 concentration rise together, plants are able to adapt to the rising temperature and experience no ill effects. Under such conditions, plants living near the heat-limited boundaries of their ranges do not migrate poleward or upward towards cooler regions of the globe. At the other end of the temperature spectrum, plants living near the cold-limited boundaries of their ranges extend their ranges into areas where the temperature was previously too low for them to survive. They actually expand their ranges and overlap the similarly-expanding ranges of other plants, thereby increasing local plant biodiversity, which in turn supports increased wildlife diversity.

Amazingly, the bulk of the scientific studies that prompts media scare stories, such as those that filed the April 3, 2006 issue of TIME magazine, actually support the opposite of what often is claimed. Rather than suggesting earth's biosphere is about to suffer irreparable damage as a result of past natural warming and future predicted warming, research substantiates nearly everything known about the beneficial effects of atmospheric CO2 enrichment on plant physiology. These studies portray a biosphere of increased species richness almost everywhere on earth in response to global warming and the increase in atmospheric CO2 concentration of the past century and a half that has promoted an expansion of species' ranges throughout the entire world.

Extinction

It is important to recognize that if recent changes in earth’s climate are stressing flora and fauna to the point of extinction, then natural changes in climate from year-to-year and decade-to-decade already should have killed them. Annual and decadal fluctuations are much more dramatic than the changes in average temperature observed to date. For example, if annual or decadal climate variations threaten life forms, then the huge temperature swings that occurred multiple times during the past 400,000 years (Figure 5) should already have killed off all life on earth. Obviously, such is not the case.

Nature responds differently than do models of nature’s response, as Drs. Sherwood and Craig Idso report:

“Of course plants could migrate poleward and upward at the poleward and upper bounds of their ranges, as new territories that were too cold for them in the past became more hospitable; but their warm-edge boundaries would not need to change. Likewise, there would be no need for changes in the warm-edge bounds of the ranges of animals that depend upon specific species of plants for their sustenance. And, in fact, this is precisely what scientists are discovering where there has been regional warming over the past several decades.”

In a study of shifts in the ranges of more than half a hundred European butterfly species over the past century, for example, Parmesan et al. (1999) found that most of them extended the northern boundaries of their ranges further north in response to a regional warming of approximately 0.8°C; but the southern boundaries of their ranges remained unchanged. Likewise, Thomas and Lennon (1999) studied an equally large number of British bird species from 1970 to 1990, finding that the northern boundaries of species residing in the southern part of Britain shifted northward by an average of 19 km, while the southern boundaries of species residing in the northern part of the country shifted not at all. Hence, rather than being forced to migrate and being nudged closer to extinction in response to a local increase in temperature during a period of increasing atmospheric CO2 concentration, these many butterfly and bird species actually increased their ranges and became even more protected from the possibility of extinction.

Similar phenomena have been observed in the sea. In a detailed analysis of benthic foraminifera (amoeba-like seal-dwelling organisms) in the Northeast Pacific, Cannariato et al. (1999) evaluated a sediment core to determine the effects of a number of rapid climatic changes over the course of its 60,000-year record. They found many periods of rapid temperature change, but no extinctions. In fact, they determined that the benthic ecosystems they studied "appear to be both resilient and robust in response to rapid and often extreme environmental conditions," concluding that "broad segments of the biosphere are well adapted to rapid climate change."

Nowhere can there be found a listing of all the species imagined to have gone extinct during warming over the last two centuries. On the other hand, a richness of new species continues being discovered, such as the recent find reported in the mountain rainforests of New Guinea. New species of birds, frogs, butterflies and palms were cataloged and include:

• Twenty new species of frogs
• Four new butterflies
• Five new species of palms
• The world's largest rhododendron flower
• New birds such as the wattled honeyeater; breeding grounds of the golden-fronted bowerbird and Berlepsch's six-wired bird of paradise which were thought extinct.
• A new species of tree kangaroo as well as six species of others that are rare elsewhere.

The current issue of TIME magazine ominously tells its readers to be “very worried” about polar bear extinction. Their source is likely the World Wildlife Fund. The problem is, reports like these have one intended conclusion:

Climate change is bad (especially for polar bears). Thus, any observed associations – as apposed to model scenarios -- between polar bears and climate change are typically ignored if they don’t show the intended patterns. That is precisely the case in this instance.

Case in point, in the Baffin Bay region (the area between North America and Greenland), the temperature has been decreasing and the polar bear populations there have been in decline. In the region with the greatest temperature increase – the Pacific region between Siberia and Alaska – nearby bear populations in the North and South Beaufort Sea (just north of Alaska) have risen. Bear population and temperature have been relatively stable throughout the remaining areas. In other words, the observed relationship between temperature and bear population is the opposite of what the WWF and Time magazine reports would lead readers to believe.

Truth is that the diversity of life on earth is mute but dramatic testimony that plants and animals are readily adaptable to variations in climate. Life forms on earth actively respond to climate fluctuations with changes in their behavior and location. To paraphrase Mark Twain, “rumors of their demise are greatly exaggerated!”

For a full-length paper on the question of warming and species extinction, see (http://www.co2science.org/scripts/Template/0_CO2ScienceB2C/pdf/extinction.pdf).

Pergerakan Ikan

Bisikan Laut Kepada si Penguntit Ikan
Sapto Pradityo, Ahmad Fikri
Tempo (35/XXXIV/13 - 19 Oktober 2006)

LIPI membuat pelacak ikan akustik yang jauh lebih murah, tapi tak kalah akurat dibanding satelit. Laut selalu membisikkan rahasianya kepada Tasman. Salah satu bisikannya adalah tempat para ikan berkumpul. Maka, dengan tangan kosong, Tasman bisa membawa pulang banyak ikan.

Kabar gembira, Pusat Penelitian Elektronika dan Telekomunikasi berhasil menjiplak telinga nelayan di pesisir Tegal itu. Pusat riset di bawah Lembaga Ilmu Pengetahuan Indonesia itu membuat peranti penguping berbasis gelombang akustik untuk membuntuti dan memetakan pergerakan ikan.

Penggagasnya adalah Dadan Muliawandana, 38 tahun. Ia yakin teknologi sangat bernilai untuk membantu nelayan. Terutama karena orang dengan kemampuan seperti Tasman kini nyaris punah.

Dulu, Tasman menangkap ikan di sepanjang perairan pantai utara Jawa, Selat Makassar, hingga Laut Cina Selatan, cuma berbekal insting. Hasilnya kerap melecehkan peralatan canggih seperti penentu posisi geografis berbasis satelit (GPS), fish finder alias penemu ikan berteknologi sonar, dan aneka peralatan lainnya. Faktanya, dia dua kali berturut-turut menyabet gelar nelayan paling produktif di pelabuhan ikan Tegal, yakni pada 1989-1990.

Tak cuma itu nilai penting teknologi ini. Di laut, siapa tak tahu bahwa nelayan Indonesia mesti berebut ikan dengan nelayan Malaysia, Thailand, hingga Taiwan. Padahal, para nelayan dari negeri jiran itu dibekali kapal berkapasitas besar dan teknologi lebih maju.

Belum lagi kondisi beberapa perairan yang ikannya sudah kelewat tereksploitasi, sehingga area perburuan ikan mesti diperluas. Walhasil, seperti diakui Tasman, nelayan perlu teknologi untuk mengetahui bagaimana pola rombongan ikan itu bermigrasi, agar pulang membawa hasil melimpah. "Sekarang tidak ada nelayan yang mau melaut kalau (penentu posisi) GPS-nya nggak jalan. Sekalipun sudah berlayar satu atau dua jam, kalau GPS-nya rusak mereka pasti kembali ke pelabuhan," ujar nelayan yang kini sudah menjadi juragan kapal itu. Padahal, GPS tidak murah.

Teknologi penguping LIPI jauh lebih murah dibanding teknologi berbasis GPS dan teknologi pelacak ikan lainnya. Salah satu alasannya, "karena tidak perlu memesan slot kanal frekuensi satelit," ujar Dadan, yang menjadi ketua tim teknologi alat ini. Pemetaan migrasi ikan dengan gelombang akustik pun memungkinkan diperoleh data lokasi setiap saat.

Ketika dijajal di Waduk Saguling, Pantai Pangandaran, dan perairan Pantai Cirebon, penguping akustik LIPI menunjukkan hasil memuaskan. Akurasinya tidak kalah dengan teknologi satelit, dengan tingkat kesalahan pembacaan alat paling besar hanya 10 meter.

Toh, Dadan masih belum puas. Dia berharap tingkat kesalahan ini dapat ditekan hingga kurang dari 1 meter. "Tapi itu sulit sekali dan sepertinya tidak mungkin," ujarnya.

Inti dari "telinga" LIPI adalah sebuah chip pemancar gelombang akustik yang ditanam di ikan yang hendak dipetakan. Chip itu berukuran satu ruas jari bayi, seberat 0,2 gram. Gelombang suara yang dipancarkan chip akan ditangkap oleh tiga hidrofon yang dipasang di pelampung. Hasilnya bakal muncul dalam bentuk lokasi ikan tiga dimensi.

Data mentah ini dipancarkan ke pusat pengolahan data, dan didapatlah peta lokasi ikan itu. Dari data-data yang terkumpul, dapat diketahui bagaimana pola pergerakan ikan jenis tersebut.

Sayangnya, alat ini tak dapat dipakai untuk semua jenis ikan komersial. Rentang jangkauan gelombang akustik tidak jauh. Chip pemancar gelombang akustik paling jauh bisa melontarkan suara hingga jarak 1 kilometer, sedangkan daya tangkap hidrofon berkisar 2 kilometer. Jelas, teknologi ini tidak mungkin digunakan untuk memetakan pola pergerakan ikan komersial dengan kemampuan jelajah tinggi, seperti tuna.

Apa boleh buat. Untuk membuntuti ikan lintas perairan seperti tuna dan hiu, solusinya adalah teknologi satelit. Inilah teknologi yang dapat dipakai memetakan migrasi ikan hampir tanpa batas, namun mahalnya tak kepalang.

Tim peneliti Universitas Stanford, Amerika Serikat, telah menggunakan teknologi satelit itu untuk memetakan pola migrasi hiu. Mereka memasang dua jenis chip pada hiu. Pertama, chip Smart Position-Only Tag (SPOT) yang ditanam pada punggung, untuk menentukan posisi hiu sepanjang waktu. Saat hiu muncul di permukaan air, chip akan mengirimkan gelombang mikro ke satelit.

Peneliti tinggal mengunduh data yang ditangkap satelit dan memantaunya dari hari ke hari. "Saya biasanya mengecek posisi hiu di pagi hari sambil minum kopi di teras rumah," ujar Barbara Block, kepala tim penelitinya.

Chip kedua, Pop-Up Satellite Archival Tag (PAT), berfungsi mengumpulkan data tekanan dan temperatur air yang dilintasi hiu. Chip kedua ini biasanya diprogram pada jangka waktu tertentu akan melepaskan diri dari badan hiu. Dari data yang dikumpulkan kedua chip ini, dapat diketahui bagaimana hiu bermigrasi.

Lewat satelit, tim Universitas Stanford berhasil membuntuti hiu selama 640 hari dan menempuh lintasan sepanjang sekitar 18.215 kilometer-hampir setengah keliling bumi. Salah satu kesimpulan yang diperoleh adalah saat bergerak ke selatan bagian bumi pada musim panas, ikan hiu menyelam di laut dalam untuk menghindari panas di permukaan air.

Agaknya, pada akhirnya teknologi LIPI dan teknologi satelit perlu bahu-membahu dalam menyediakan peta ikan karena masing-masing memiliki kelebihan dan kekurangan. Tujuannya cuma satu: agar nelayan dapat memantau di mana, misalnya, ikan kerapu berkumpul saat musim panas. "Jadi, tidak lagi hanya bermodal naluri saat meninggalkan pelabuhan menuju laut lepas," kata Dadan.

Agar seluruh nelayan dapat memanfaatkan data pola migrasi ikan, Dadan berpikir data tersebut perlu dimasukkan ke Internet. Dengan peta pergerakan ikan di komputer dan penguping setia mengintai keadaan di bawah laut, sepertinya nelayan tinggal menunggu ikan-ikan itu lewat.