- Definizione, prove geologiche e le cinque grandi estinzioni finara note.
- Valutazione critique: segnali della siesta estinzione e dibattito scientifico sui tassi reali.
- Sette possibili cause future: dal Sole ai vulcani, thin all'impatto umano.
- To mitigate the risk of conservation, reduce pressure and monitor migliori.
This route lasts around 4,5 milliards every year, the Earth has già vissuto almeno cinque grandi estinzioni di pasta and, secondo molti ricercatori, we could once again experience it in the middle of a siesta. Questi episodi non somno semplici scomparse sporadiche di specie, ma periodi in cui la loss of biodiversity accelerates sharply its global scale in geologically brief time.
To frame the phenomenon, I just had to think about it 98% of organisms che ha popolato il pianoeta non esiste più. In “normal” conditions, the seventh classic indicates a medium of 0,1–1 specie between 10.000 specie per secolo; I don't even have a big event, I'm invece, if you arrive with your partner, come there 75% of the species perse in less than 2,8 million a year, in an even global distribution. And no, it's not just theory: rocce e fossili raccontano this story con dovizia di dettagli.
It's a massive mass event
A mass-continuous event (EEM) is defined when the species I compare very quickly say how much vengano sostituite. According to the Natural History Museum of Londra, speaking of a crisis, it touches on around three quarts of this species in a brief geological time, fully enters the “massive” category. The chiave characteristic is the planetary tension: it comes from the paleontologist Mario Cozzuol (UFMG), this event occurred globally and relatively quickly on a geological scale.
Gli indicator that allows us to derive profits from analysis rock formations, chimica dei sedimenti e fossil record. Geologi, paleontologi e biologi combine no datazioni e confronti qualitativi nel tempo per vedere chi sopravvive e chi no. If a species completely disappears from the stratigraphy of a certain soglia temporale, it's a strong signal di estinzione.
Le “Big Five”: the 5 great highlights of the story
I didn't register geologici emerging with five colossal episodes. I understand this has a risk to the ecosystem, I learn to spend time with a new group of people living and constantly learning the chapter from the beginning.
1) Ordovician–Silurian (circa 440 million years ago)
The world was dominant in the marina and in stavano comparing it prime piante terrestri. Yes, in the first place, scomparve circa l'85% delle specie, in particolare piccoli invertebrati marini. Tra le cause proposal: the spostamento di Gondwana verso il polo sud, glaciation, marine waterfall and sudden temperature variations. Il raffreddamento globale e il ritiro dei mari ridussero habitat chiave, innescando la crisi.
2) Devonian (370–360 million years ago)
Un mondo con tanti primitive fish, i primi vertebrati terrestri a quattro arti, gli insects and always piante più alte. In this dispute, several episodes of the crisis were shared by all 70–80% of the species. Fra le ipotesi: oscillazioni climatiche (broth/freddo), variation of the livello del mare, diminuzione dell'ossigeno atmospheric and oceanic, and persino possibili impatti cosmici. Le taste suggestiscono a mosaic of factors I'm sorry for a simple cause.
3) Permian (circa 250 million years ago)
La peggiore di tutte, chiamata non a caso "The Great Death": if you appreciate it remaining there 95% of the species. The Earth was living in the formation of a supercontinent Pangea, with intense volcanic activity, climate risk and ocean acidification. Alcune ipotesi chiamano in causa gigantic eruzioni (Siberian Traps), increase in CO2, oceanic tossici and, secondly, an asteroid impact. In this case, collasso degli ecosistemi fu totale e la biodiversity impiegò decine di milioni di anni per riprendersi.
4) Triassic (circa 200 million years ago)
Nel Triassico compaiono i primi dinosauri hey primi mammiferi; pinacee and more gymnosperm if it's different. Well, a new event: it appears around here 76% of the species. The separation of Pangea, with imposing volcanism and strong CO2 emissions, opens the door to ocean acidification, climate instability and habitat loss. Paradossally, i dinosaurs superstiti trovarono condizioni favorevoli per espandersi and dominatee il Mesozoico.
5) Cretaceous (circa 65–66 million years)
It's the first note: coinvolse soprattutto i dinosauri non aviani (sopravvive la linea degli uccelli). Compaiono circa there80% of the species. The first accreditation is the impact of a asteroid in the penisola of the Yucatán (crater of Chicxulub), it contains a catena of events: darkening, duct of photosynthesis, Piogge acid, volcanic activity (Deccan Traps), thin at the collasso delle reti trofiche. I piccoli organismi che richiedevano pochi nutrienti Ebbero migliori chance di resistere, aprendo la strada alla grande radiazione dei mammiferi.
Uneventual “prime” destination: l'Ediacarano
Alcuni studi suggests there is no possibility of using an anchor mass in the first place, in Ediacaran period (around 550 million a year), with lost money80% of the species. It provides evidence that oceani greatly improves ossigeno, in favor of organisms adapting to basse concentrationzioni di O2. Here I ended up figuring out how to eat Obamus coronatus e Attenborites janeae. However, let me know what I said: mancano anchor prove enough to equate it to the other “Big” cinque.
Are we still living la siesta estinzione di pasta?
Diverse science ritengono che l'umanità stia guiding one sista estinzione, accelerating it in comparison with 100 to 1000 turns rispetto al “fondo naturale” from there primi ominini. The main cause of human impact: soil use change, transforming over 70% of the earth's surface, used daily 3/4 of the sweet water, intensive agriculture, inquinamento and habitat frammentation. The ciò is only the emission of CO2 from fossil fuels, with global warming, siccità, alluvioni and altre catastrofi.
As emphasized Fabrício Rodrigues dos Santos (UFMG), the current rhythm seems very quick as seen in the early crisis since the Cretaceous. However, studios come to Cozzuol richiamano alla prudenza: la temporal resolution With my leggiamo the present and the past it is diverse, and confronting the epoche lontanissime involves much uncertainty.
An analysis published in PLOS Biology has proposed a less apocalyptic literature: evaluating 163.022 species and concentrating on itself genres dal 1500 in poi, gli autori (John Wiens and Kristen Saban) stimano 102 generi estinti negli last 500 years (90 animals, 12 feet), with a significant share uccelli and mammiferi and with this thick estinzioni confined in insular habitat. The percentage rises to 22.760 generi valutati sarebbe within all 0,45 %, and it is the essence of the generi potrebbero perfino essere rallentate nell'ultimo secolo.
This vision contrasts with other labor (and in many cases, its 5.400 vertebrate genes) which sees an accelerated pace and speech tightly sista estinzioneScholars like Conrad Labandeira I distinguish between “crisis of biodiversity” and “estinzione di mass”, evidencing that the first is real, while the second is anchoring an interpretation. In frattempo, documentare le estinzioni resto difficile, soprattutto per invertebrati, piante e funghi meno studiati (Stuart Butchart, BirdLife International).
Ci sono poi stime (spesso dibattute) che, negli anni 2000, ipotizzavano migliaia di specie perse l'anno, thin at 14–70 al giorno, with strong gap per tutti i gruppi little conosciuti. It's a complex picture: The loss of biodiversity is undeniable, ma stabilire con rigore se abbiamo già superato la soglia “da manuale” di un event di mass richiede prudenza metodologica e dati più completi.
Come i richeratori ricotruiscono queste crisi
Gli scientific data and interpretation rocce e fossili per tracciare chi attraversa le soglie temporali e chi scompare. If in a stratigraphic sequence an evolutionary line is interrupted, something serious è accaduto all'ambiente. Gli stessi confines to grandi ere geologiche (Paleozoic, Mesozoic, Cenozoic) sono spesso segnati da estinzioni diffuse; in practice, geological time If you “seziona” thank you for the great change in biodiversity.
In the present, look back at the fossil, as long as we monitor it populations, tendenze di habitat e global database (ad example in the Liste Rosse). But the big story remains to be documented and lost to the “invisible” group, which I sleep for a large part of my life on Earth: senza dati solidi, si rischia di sottostimare (o sovrastimare) la crisi.
Le 7 causes potenziali che potrebbero innescare nuove estinzioni di massa
Oltre alle cinque grandi estinzioni storiche, la letteratura scientifica elenca possibili inneschi futuri in grado di change all in a relatively quick time. That said next, sette scenari ricorenti in this value of global risk.
1) The Sun
Our star is not a passive actor: in the meantime he ends up increasing his own brightness, favoring the oceani evaporation. Già oggi, I happened to eat it coronal mass ejections (CME) I can't bombard the Earth with cariche particles, causing a blackout, causing satellites and possibly cascading effects sulle technological society. Pursuing the first step of indirect risk, in the extreme scene of the Sole potrebbe innescare climate changes rapidi e destabilizzanti.
2) Geomagnetic inversions
The inversion of polymagnets avvengono periodically in terrestrial history. During the transition, it magnetic field può indebolirsi, lasciando il pianoeta più exposed to the solar wind and all cosmic radiation. Gli effetti esatti sono ancora dibattuti; In theory, a large field deboles prolungato potrebbe amplify atmospheric erosion the danneggiare biosphere sensibili. The science does not have a complete consensus on whether it can achieve biology, but it is considered a topic fattore di vulnerabilità.
3) Asteroids and comets
Gli impacti sono a rare but concrete minaccia. We see the legacy of the Yucatán asteroid and the crisis the late Cretaceous period. I collected the ice cream in a large part of the catalog NEO (Near-Earth Objects) pericolosi, but there remains a non-transparent fraction of the celestial body anchor unknown. A sufficiently large event could be scatenare winter of the impact, prolungate darkening, collasso of food catene and acidification.
4) Il mare (methane clatrati, anossia, oceanic chemistry)
Gli oceani has an arsenal of potentially devastating processes: the explosive explosion of methane intrappolate nei clatrati (“clathrate gun”), oscillazioni estreme del sea level, squilibri chimici e eventi anossici di ampia scale. Questi phenomeni puedo no ristrutturare gli ecosistemi marini alla radice e, rivésso, travolgere anche la earthly life that depends on the oceanic trophy.
5) Vulcani
Grandi province magmatiche e super-eruzioni sono associated with numerous EEM. Massive emission of carbon dioxide and composed of the zolfo may not cause pyogge acid, warm-up (the, temporarily, raffreddamento) globale, acidificazione degli oceani e vere e proprio ecological cares per collasso of photosynthesis. Part of the volcanism is monitorable, but many scenes remain unpredictable.
6) Riscaldamento and global raffreddamento
The grandi is the passenger seat if it sleeps thickly with accompaniment to climate changes quickly. The risk, in particular, amplifies the effect of the mountains with water vapor, destabilizza gli oceani (anossia), ridisegna biomi e idrologia. Il raffreddamento può essere altrettanto traumatic, ma la letteratura sottolinea che il extreme heat its global scale is a “killer” that is both efficient and long-lasting.
7) Noi stessi
L'umanità is a geological agent. Dalla global nuclear war there change climatici indotti, from the loss of habitat to the diffusion of invasive species, thin to sovrasfruttamento and all'inquinamento, we can innescare sistemiche crisis. Il rischio maggiore is thereDomino effect: a moderate natural event, combined with anthropic pressure, overcomes criticism and accelerates itextinction on a large scale.
You, dati and caution: come leggere il presente
The scientific debate is alive. Musei come il Natural History Museum di Londra e l'American Museum of Natural History sottolineano lo schema storico delle estinzioni, entre studiosi in Brasile (UFMG), negli Stati Uniti e nel Regno Unito aggiungono tasselli its cause and tempistiche. Ricercatori come Wiens and Saban invite us to consider the taxonomic livello (species vs. gender) and geographic bias (strong weight of islands), which is also evident in the current trend colpiscono there nostra sicurezza alimentare, idrica and economica.
Come thick and fast, I numbered on the button: let it last perdite annue The species varies from the southern assumption to the total number of resistant rates (wide range 20–100 million). However, it is undeniable la pressão umana suoli, acque e clima stia comprimindo gli spazi vitali di migliaia di organismi. Here if you chiami Anthropocene or if you prefer a conservative literature, in the framework impose action concrete conservation and mitigation.
Guardando al quadro generale, gli EEM hanno più cause, species concomitanti: tettonica, impatti, vulcani, chimica degli oceani, clima e dinamiche biologiche. At present, the question of the cocktail itself is scelte e politiche Humane, capable of making differences between resilience and collasso. Good news? I intervened in the decision of guardianship, ripristin and riddance of his issuance stanno già salvando generi and famiglie; The sfida now is scalarli with urgency and intelligence, prima che nuove soglie critiche vengano superate.
