1.Khai niem:Tuyet chung co nhieu y nghia va khac nhau tuy thuoc vao tug boi cah cu the.1 loai bi coi la tuyet chug khi k con 1 ca the nao cua loai do song sot tai bat ki noi nao tren TG.Neu nhu 1 so ca the cua loai do con sot lai chi nho vao su nuoi duong cua con ng thi loai nay bi coi la tuyet chung trog thien nhien hoag da.Trog ca 2 trg hop tren thi cac loai co the coi nhu bi tuyet chug trog tren fam vi toan cau.Mot loai bi coi la tuyet chug cuc bo neu nhu chug k con sog sot tai noi chug tug sih sog nhug ng ta van tim thay chug o noi khac trog thien nhien.Loai bi tuyet chug ve fuong dien sih thai hoc khi so luong ca the loai con lai it den noi tac dung cua no k co chut y nghia ji' voi nhug loai khac trog wan xa.Khog fai toan bo cac loai deu co muc do tuyet chug nhu nahu.Cac loai de bi tuyet chug nhat:

+Co vug fan bo hep,noi sog dac trug

+Chi ton tai vs 1 hay vai ưan the

+Kik thc ưan the nho hay mat do ưan the thap

+Co ưan the dag suy jam ve so lg

+Loai can 1 vug cu tru lon

+Co kik thc co the lon

+Di chuyen k tot

+di cu theo mua

+It co tinh bien di di truyen

+Loai dac trug chi sog o moi trg on dih

+Song thanh bay dan

+La doi tg san bat cua con nguoi

2.Tuyet chug la 1 qua trih tu nhien:Theo thuyet tien hoa. loai bi day den tuyet chug khi k cah trah noi thuc an va moi trg sog hay bi loai khac an thit.1 loai co the tien hoa tu 1loai khac de dap ung vs nhug thay doi cua moi trg hay do su thay doi ngau nhien cua quy gen.Neu toc do cua viec hih thanh loai tuog duog hay vuot wa toc do tuyet chug thi' da dag sih hoc dc duy tri hay tag len

3.Tuyet chug do con ng gay nen:Tac dog dau tien do la su jam sut cac loai thu lon o Uc,Nam va Bac My vao thoi jan ma che do thuc dan bat dau o luc dia nay hang ngan nam trc.Nguyen nhan truc tiep la do san ban,jan tip la khai hoag,dot rug.Nhieu loai chua bi tuyet chug nhug bi hao hut rat nhieu do cac haot dog cua con ng va chi ton tai vs so lg rat thap ,dc coi la tuyte chug sih thai vi vai tro cua chung k con trog wan xa,tg lai cua chug k chac chan.Cac so lieu:

24% loai thu dag doi mat tuyet chug.12% loai chim de doa tuyet chug trog 100 nam nua.1/4 bo sat va 1/3 luong the de doa tuyet chug...

Nguyen nhan cua su tuyet chung

1.Su fa huy noi cu tru:Mat noi cu tru la nguyen nhan dau tien khien cho cac loai dog vat co xuog sog bi tuyet chung va keo theo ca dong vat k xuog sog ,thuc vat,nam...

+Cac rung mua nhiet doi bi de doa.Viec fa huy rug mua nhiet doi la dau hieu di kem voi viec mat cac loai.Hang nam co khoang 180.000 km2 rug mua bi mat,80.000 km2 bi mat hoan toan,100.000 km2 bi suy thoai den muc thay doi cau truc loai va dien the sinh thai.Hau het la bi fa huy do khai hoag lay dat san xuat nog nghiep

+Rug kho nhiet doi:Dat dai tai vug nay thik hop cho ptrien nog nghiep va chan nuoi ja suc.Dan so tap trug o day cao gap 5 lan so vs rug mua nhiet doi nen rung bi fa huy cao hon.

+Dat ngap nuoc:La noi cu tru wan trog cua cac loai dong vat thuy sinh,chim nuoc va la noi dieu tiet nc,cung cap nc uong...Hien nay dat dc khai thac de de fuc vu cac muc dich fat trien hoac bi o nhiem hoa chat.

+Rug ngap man:La dag he sih thai wan trog nhat vug nhiet doi,la noi sih san,kiem an cua nheiu loai tom,ca.Day cug la noi cug cap go,than cui cho nganh cog nghiep.Rug ngap man dag bi fa huy do viec khai thac chat fa nuoi trog thuy san.

+Hoang mac hoa:Rat nhieu cac wan xa sih vat sog trog cac vug khi hau kho han theo mua da bi suy thoai va dat dai tro thanh hoang mac ma nguyen nhan la do cac hoat dog cua con nguoi.Ban dau cac vug dat nay rat fu hop cho viec fat trien nog nghiep,nhug viec gieo trog lien tuc lam cho dat bi xoi mon,mat kha nang giu nc.Tham co lien tuc bi trau,cuu,de an trui.cac cay than go bi khai thac lam cui.Hau qua la be mat dat mat lop tham thuc vat che fu bi hoang mac hoa.Tren Tg co khoag 9tr km2 bi kho han dan den hoag mac hoa nhu tren.

2.Cac noi cu tru bi chia cat,cach ly:Lam tang kha nang xam nhap cua cac loai ngoai lai va bug no so lg cac loai con trug dich hai va ban dia.Fa huy noi cu tru se han che kha nang fat tan loai ,kha nang kiem moi cua cac loai thu.Gay suy jam wan the dan toi su tuyet chung.

3.Noi cu tru bi fa huy va o nhiem:Dang fa huy nguy hiem nhat la o nhiem moi trg

+O nhiem do thuoc tru sau:Thuoc tru sau lang dong trog dat hay tich tu trog co the sih vat.Lam anh huog den cac loai chim an con trug va cac loai dog vat khac.Khi nog do thuoc doc tinh lon tich luy den muc cao trog sih vat nhu cac loai chim thi chug yeu di va de ra nhug wa trug vo mong?de vo~ trog wa trih ap.Do vay lam suy jam quan the loai chim.Ngoai ra con anh huog den cac loai ca,do nguon nuoc bi nhiem doc.

+O nhiem nuoc:Do con ng lam o nhiem wa viec thai cac chat thai cog nghiep,sih hoat,chat tay rua... vao moi trg nuocCac chat thai vao moi trg nc se dc lan toa di rat xa.Cac chat thai sih hoat cua con ng thai vao moi trg luog qua lon khoang chat vi va da luog gay hai neu chug co nog do cao.

+O nhiem khog khi:Cac hoat dog cua con ng lam o nhiem kk:Mua axit:Cac nganh cog nghiep luyen thep,nhiet dien...su dug than hay khi dot tao ra NO3,SO4 vao kk.cac khi nay gap hoi nc tao nen axit lien ket voi cac dam may thanh mua axit..Giam ph trong ao,ho,dat...giam so lg lg~ cu,chet ca con...

+Su thay doi khi hau toan cau

4.Khai thac wa muc:De kiem soat tih trang nay.Su dug cac luat le nhu chi dc san ban trog 1 khu vuc,cam san ban con cai,con non...de dam bao cho khai thac va fat trien ben vung.

5.Su du nhap cac loai ngoai lai:

+Su van chuyen co chu dich:Khi nguoi chau au den 1 vug thuoc dia,ho mang theo nhug vat nuoi ua thik.hoat dong nong lam nghiep gay fat tan cac loai thuc vat,dog vat..Nuoi trog thuy san gay ra su lay lan cua loai ca.Fan lon loai du nhap k sog dc o noi moi den.Nhung van co 1 so loai con vuot troi so vs loai ban dia,cah tranh,an thit loai ban dia dan den loai ban dia de doa tuyet chug.

+Su van chuyen k chu dich:Cac loai dog vat tu bo len cac container hang hoa den cac luc dia khac thog wa hoat dong van chuyen cua con nguoi

6.Su lay lan dich benh:

Cac loai benh lay lan la moi de doa lon voi nhieu loai quy hiem.1987,wan the cuoi cung cua loai chon' chan den trog tu nhien da bi tieu diet boi virus gay benh sot ho cua cho' nha' va 1 so ja suc khac.Ly do:

+Cac loai dc con ng nuoi va dog vat trog tu nhien khi song trong wan the mat do cao thi' co nguy co mac cac benh dich hay ki sih trung.

+Tac hai jan tip cua su fa huy noi cu tru

+Tai cac khu bao ton,cac loai gap va tiep xuc rat nhieu loai ma trog dieu kien tu nhien chug k he gap nen beh dich co the truyen sang cho nhau