Các hệ sinh thái cửa sông: Những đặc trung cơ bản, tài nguyên và định hướng cho việc phát triển bền vững

Nội dung text: Các hệ sinh thái cửa sông: Những đặc trung cơ bản, tài nguyên và định hướng cho việc phát triển bền vững

1. KHOA HOC CONG NGHE CAC HE SIIMH THAI CIJA SOIMG: IMHUIMG DAC TRUIMG CQ BAIM, TAI IMGUYEIM VA DflMH HUQIMG CHO VIEC PHAT TRIEIM BEIM VUIMG Vfl Trung Tangi T6MTAT Noi dung bai bao gioi thieu nhung dac trung co ban ciia mot dang thiiy vuc chuyen tiep o vung bien nhiet doi: he ciia sdng, trong dd chiia dung nhung sinh canh dac thii vdi nhimg loai sinh vat cd ngudn gdc bien, rdng nhiet va rdng mudi da tao nen nhiing dang tai nguyen to ldn cho su phat trien kinh te-xa hdi cua cac tinh duyen hai. Thd manh cua viing cita sdng gdm dat mdi bdi va cac san pham cua dat, tai nguyen da dang sinh hpc, cung nhu tidm nang phat trien giao thdng, mo mang du lich sinh thai. Hon niia the ky qua, hang van ha dat mdi ria cac chau thd dugc chinh phuc nhd quai de lan bien. Nghe khai thac bien, trudc het la khai thac va nudi trdng hai san da cd nhiing ddng gdp quan trpng cho nen kinh te qudc dan. Tuy nhien, mat trai cua nd la khai thac cdn chira dung nhieu yeu td bat hpp li va kem ben vung: quai de lan bien d at, thieu qui hoach, lam xao trdn canh quan, gay lang phi tai nguyen; khai thac hai san qua miic, nudi trdng thuy san thieu su quan li, chat lupng mdi trudng suy giam do dd, de lai nhieu hau qua sinh thai khdng kem nang ne nhu bd lai dat hoang hda do quai de khdng thanh, thu hep rimg ngap man (RNM), gay d nhidm mdi trudng Truo'c thuc trang dd, bai bao neu len nhtrng nguyen tic va nhiing dinh hudng co ban cho khai thac va sir dung tidm nang dat dai va da dang sinh hpc viing cira sdng mdt each hpp li cho su phat trien kinh te - xa hdi mdt each bdn vung. Tir khoa: He sinh thdi cua song, phdt trien ben vitng. Cke he ciia song (CS) 11 noi chuyen tiep giiia Cic he CS dang trong trang thai phit trien nuoc ngpt vl nuoc man, a do nuoc ngpt hoa trpn co thong qua boat dpng boi tii-blo mon hoac dat lan miic dp voi nuoc man do boat dpng ciia thuy trieu. bien hoac bien lln dat va dly bien dpng, do do chtia Vtmg CS la mpt bp phan ciia doi bien ven bo (coastal dung nhieu riii ro tiem an, doi khi rIt khoe het doi zone), nlm trong truong tuong tie giQa luc dia-dai voi doi song con nguoi. duong-khi quyen ma true tiep la tuong tic song-bien. Dieu kien song cua vung CS, nhlt la dp muoi Bo bien nuoc ta trai ra gin 13 vl dp vl bi chia cit luon bien dpng trong bien dp Ion, ttr 0,5 den 30(32) thanh timg doan boi cac he thong song, tii do hinh %o voi toe dp nhanh theo khong gian vl thoi gian, thinh nen vung CS rpng Ion, hlu nhu 6m lly toln bp phu thupc vao cic chu ki mfia cua khi hau (mua lu vl khoi nuoc ven bo. Dpc bo bien, he CS co the gom cic kief tren cac song) vl chu ki thuy trieu. dang sau: Cic CS chau tho, CS hinh ph^u, chuoi dim Phan bo trong vting CS 11 nhting loli sinh vat pha ven bien mien Trung, vung vinh nong ven bo vl rpng nhiet vl rpng muoi, hinh thanh nen cac nhom cic sinh lay ngap trieu dupc phti boi rung ngap man sinh thii dac trung: nhom sinh vat nuoc ngpt thich (RNM) 6Tay Nam bp [8]. nghi voi dp muoi thap o phin diu CS, nhom sinh vat I. niHUniG DAC TRUNG Cff BAN CUA CAC HE CUA SONG CS chinh thiic, nhom sinh vat bien rpng vl hep muoi 1. Nhiing tinh chit ehung xam nhap vio vung thIp CS vl nhom sinh vat di cu qua CS (di cu song-bien hoac bien-song) de sinh sin Cic CS CO tuoi lich su tre hon so voi nhieu he ttt (Vu Trung Tang, 1994). nhien khic. Su ra doi ciia cic he CS hien dai gin lien voi lich su hinh thinh bo bien, khoing duoi 2000- Khu he sinh vat CS co tuoi Uch su tre hon so voi 3000 nam ve truoc. Dieu nly co anh huong quyet cic khu he phan bo a eke he sinh thii khic tren can dinh den qua trinh thich nghi vl tien hoa ciia cic loai hoac bien, chu yeu co nguon goc bien. Do do, so loli song trong vung. thich nghi dupc voi dieu kien song a vung CS khong nhieu, nhung o day nho tiitra huong nguon tiiu'c an phong phu, it ke tiiu chung thuong phat tiien hung tiiinh ve so lupng, tao nen san lupng cao cho khai thac. GS. TS. Dai hpc Qudc gia Ha Ndi NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009
2. KHOA HOC CONG NGHE khi tiitu cudng Vung CS nhu mpt cai bIy, bIy vio day nguon muoi khoing va chat htfu co tir luc dia dupc cac dong song mang ra hoac fit bien mang vao va dupc hinh thinh fai ch6, trong do mun ba htfu co dong vai tro quan trpng nhlt cho cac loai an mun ba (detritivore), NGHi CA mpt nhom uu the, tham gia chinh vio sir chuyen hoa vat chit va nang lupng cua he cua song (hinh 1). »• Antiirctiep —^. Con duong van chuyen vat chat chinh ^ Phan giai va hoan lai duoi dang nguon thiic an hiru c o khac. 2. Nhiing die di^m riSng ciia cic dang cua song Cac duong bau due la nguon khoi dau cho cac xich thiic in Tren quan diem dpng lire cua moi tuong tac Hinh 1. Ludi thtic in die tnmg eho cic ht da song song-bien, ngoai nhtfng tinh chit chung nhat nhu nhi$t ddi, gom xich thtic in chin nuoi, xich mun bi hthi neu a tren, cac CS con dupc dac trtmg boi nhting net ca vi xidi thiic in thim thiu, trong d6 xich thti 2 dong rieng cua minh (bing 1). vai ti-6 quan trong bie nh& trong su ehuyen tii vit chit vi ning hiong trong vung (Vti TVung Tang, 1976,1999.) Bing 1. Nhiing die tnmg ca ban v6 di^u kifen tu nhi^n ctia cic ht cita song TT CAC DANG CUA SONG NHUNG DAC TRUNG CO BAN Day la viing sut lim kien tao dupc den bii. Dpng luc dong sdng Cic ciia song chiu tho: chiem uu the vdi tong lupng nudc ngpt va phii sa Ion, nudc CS bi 1 Chau tho song Hong ngpt hda manh, dat lan bien vdi toe dp cao, tao nen chau tho, cac bai va chau thd song Cuu long trieu biin cat, cac dao cira song va tien chau tho. Phan bo trong viing chii yeu la nhUng loai sinh vat nudc lp. Day la viing sut lun kien tao khong dupc den bii. Tong lupng nudc ngpt va lupng tai phii sa cua cac song thap, dong tridu uu the dua nudc man xam nhap sau vao npi dia, tao nen luc bao mdn manh ddi 2 Cic cua song hinh phSu vdi long sdng, bd", bai do dd,^cu'a sdng ngay mdt loe rdng ra bien, bien lan din dat hen. Phan bd trong viing chu yeu la nhirng loai sinh vat nudc lo. Pha dupc hinh thanh nhd su xuat hien bd' cat phia ngoai, dm lay mdt xoang nudc phia trong dupc gpi la pha, trong dd ddng sdng chay ra bien mpt each an toan. Ngoai cira cua cac con sdng, pha cd ciia rieng cua minh lien thdng vdi bien. Trong miia mua, nudc sdng ldn, 3 Cic phi midn Trtmg cac pha hoat dpng nhu nhimg ho chiia, phan bo trong pha chii yeu la nhiing loai nudc ngpt, nhung trong miia khd, lupng ddng chay thap, khdi nudc ciia pha bi man hda do nudc bien xam nhap vao; quIn xa sinh vat miia nay gom chii yeu nhirng loai nuoc Ip va lp man (meso- va polyhahne). Day la vimg dIt thap phat trien o' dong bing phu can sdng Ciiu Long vdi su thdng tri cua cay RNM. Nguon nudc ngpt va lupng phii Cic sinh Iiy ngip tridu dupc phu sa nhan tir sdng Cim Long thdng qua he thdng sdng-rach chIng 4. boi RNM a Tay Nam bp chit, hda trpn vdi nud-c bien xam nhap vao nhd boat ddng cua thuy trieu Bien Ddng va vinh Thai Lan. Sinh vat song trong vimg chu yeu la nhting loai nud-c lo. Dupc hinh thanh bdi nhieu nguyen nhan do su an sau cua bien vao npi dia, su hda tan cua cac tudng da, su ndi dao vdi bd, v.v Cac vung vinh cung cd the nhan nud'c ngpt tir mpt so sdng sudi vdi luu lupng Cac vung, vinh nong 5 thap, khdi nud'c man chiem uu the, thdng tri, do dd "che dp CS" chi venbdf xuat hien tam thdi. Phan bd trong viing chti yeu la nhirng loai sinh vat ciia khdi nud'c ven bd (neritic), chung cd the hoan thanh tat ca cac giai doan phat trien ca the cua minh ngay trong vinh. NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009
3. KHOA HOC CONG NGHE 3. Khai thic vi su dung cic dang tii nguydn ven bien lai dupc boi voi toe dp trung binh 10,8 ha/nam. Tii nguyen vung ciia song gom dat vl cic sin pham cua dat, nuoc va cac san phim tii nuoc, nguon Nhin chung, ria CTSH co khoang 20% chieu dai bo nang lupng sach (gio, thuy trieu), tiem nang phat bien bi xoi 16 voi tdc dp khi manh. Dac biet khu vuc trien giao thong vl du lich sinh thii. Chp Con-Van Ly (Hai Hau, Nam Dinh) trong 30 nam (1936-1966) dif da mat di 650 ha ti-enchie u dii 30 km, a. Ddt vd su dung ddt tdc dp trung binh 11 10-15 m/nam. Nhieu di tich nhu Str boi dip 6 ria cac chau tho 11 tien de quan mieng gieng, cong ling, thIp chuong nha thd' nlm trpng cho cong cupc quai de lan bien, mo rpng dat trong sdng nudc, cich bd tii 500 den tren 1000 m. dai. Chau tho song Hong (CTSH) co dien tich Theo mdt tdng kef khic, bd bien CTSCL cung cd khoang 15.000 km^, con chau tho song Cuu Long hien tupng tuong ttr. Phia dong, tii Ghenh Hio den (CTSCL) CO dien fich Ion gin gIp 3 lln nhu the, cue nam mui Ca Mau bd bien hi xdi Id manh, nhlt 11 khoang 40.000 km^ vl hing nam vin tiep tuc tien ra d cac huyen Dim Doi, Ngpc Hien. Trong giai doan bien voi toe dp cao, co noi den 80-120 m/nam nhu 6 1968-2004, dac biet 11 khoang thdi gian 1968-1987, fly nam CTSH hay tai cua Dai (song Tien) va fay bien da gam sau vao dat lien tii 0,5 den 2 km. Do dd, nam miii Cl Mau. dien tich dat hi mat chimg 8.367 ha, trung binh Cac kef qui khao sat cua Tran Dtic Thanh va 220 ha/nam. Ngupc lai, phia tay Ca Mau, nhlt 11 fir nnk. (2000) chi ra ring, a ven bien CTSH fir nam ciia song Bay Hip den Dat Mui, bd dich chuyen ra 1930-1965, dat dupc boi them ll 445,8 ha/nam, dien bien, noi xa nhat den 4 km, noi gan nhlt 2-3 km, nhd tich bi xoi lo la 32,33 ha/nam, can bing boi-lo la dd, dien tich dIt ven bien d day da tang len khoang +416,47 ha/nam. Nhu vay, tren 145 km chieu dai bo 7.494 ha, trung binh gin 200 ha/nam. Day 11 noi bien chau tho o giai doan nly toe dp lan bien trung dupc bdi fu manh, tao nen cho RNM phat trien vl md binh 11 28,7 m/nam. Trong thoi gian 1965-1990, dien rdng, trong khi dd doan bd tft ciia song Ong Ddc den tich boi 11 469,9 ha/nam, con lo 11 47,85 ha/nam, An Minh (Kien Giang) va tft Rach Gil den Ha Tien it cin can b6i-16 11 +422,5 ha/nam voi tdc dp lan bien cd bie'n dpng (Nguyfen Manh Hung, 2009). trung binh 29,1 m/nam. Giai dpan 1990-1998, can can Dit bai bdi ven bien sau khi chinh phuc, dupc su boi tti-xoi lo +639,7 ha/nam voi toe dp trung binh la dung vdi nhieu muc dich, chu yeu 11 noi dinh cu, md 44 m/nam, cao hon so voi cic giai dpan truoc. rpng dif nong nghiep, nuoi trdng thuy san, trdng va Ngupc voi qui trinh bdi fu 11 su xoi lo cua bo fu bd rtmg phdng hp ven bien. bien. Truoc thap ki 80 cua the ky truoc, doan bo tir Ngoai nhung ling xa mdi ra ddi d phia trong de Ciia Diem Di^n den Thuy Xuan (Thai Thuy, Thii bien, theo cac thdng ke (D6 Dinh Sam va nnk, 2005), Binh) hi bio mon ca bo vl day voi toe dp tuong ting dien tich dat ngap man ven bien dupc danh gil la la 13 m/nam vl 4 cm/nam (Vtt Trung Tang va nnk., 606.792 ha, bao gdm trong dd dat dupc phu bdi RNM, 1985), nhtmg khi RNM dupc phuc hoi, toln tuyen dat NTTS vl chua su dung dupc het ke trong bing 2. Bing 2. Phin bo di6n tichDNM , RNM vi dim NTTS ti-ongci c khu vuc a Vi$t Nam Dien tich dat Dien tich cd RNM Dien tich khdng cd Dien tich ao dam TT Khu vuc ngap man RNM NTTS ha % ha % ha % ha % Tdng sd 606.792 100,0 155.290 100,0 225.394 100,0 226.075 100,0 1 Ddng Bic 65.000 10,71 22.969 14,80 27.194 12,06 14.837 6,56 2 DB Bic bd 57.345 9,45 20.842 13,42 22.651 10,05 13.852 6,13 3 Bac Trung bp 30.974 5,10 2.300 1,48 22.167 9,83 2.505 1,11 4 Nam Trung bd 13.068 2,15 700 0,45 * * 12.368 5,50 5 Ddng Nam bd &TP HCM 67.100 11,06 26.092 16,80 37.540 16,65 3.468 1,50 6 DBSCL 373.305 61,52 82.387 53,05 111.873 49,63 179.045 79,20 Ngudn: Dd Dinh Sdm vd ct, (2005). Ddu (*) - khong thdng ke duac vi dien tich qud nho NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009
4. KHOA HOC CONG NGHE Cfing vdi tii nguyen dat vl sinh vat, vung CS cdn trudng. Nhd ngudn thiic an phong phii, vitng CS 11 cd ngudn cit, cac khoing chit, dac biet la sa khoing "vudn uom" au the cua cac loli ddng vat bien, noi chua: Oxit titan, zircon, monazit, imenhit vdi trif lupng nuong tua, lan trdn ke thu, noi kiem an va bai de cua cong nghiep. Dly cdn 11 noi phit trien cong nghiep nhieu loli, 11 ciia ngd cua cac loli di cu song-bien (cl giao thong bien (ddng va siia chtia tau, xly dung cang), chinh) hay bien-song (ca mdi, cl chay). cic CO sd che bien hai san, nhieu noi trd thinh nhifng Cac ket qua nghien ciiu ciia nhieu tac gia ve fhlnh khu an duong va du lich sinh thii hip din. phin cac nhdm loli sinh vat CS dien hinh dupc tdng b. Da dang sinh hoc hpp lai vl tiinh bIy d bing 3 {Vu Trung Tang, 1994, 2009). Ngoli sd lupng loli phong phu, trong vung CS Do lich sti hinh fhlnh, su phan hda cao ve noi cdn tdn tai cic he stiih thii va noi sdng rat dac sic: sdng, nhat 11 trong RNM, tham cd bien vl su bien RNM, tham cd bien, cic bai trieu tran, cic dao CS, bd dpng cua cic dieu kien sdng nen mtic da dang sinh dl dly hang ddng den cic ao dim NTTS, v.v Trong hpc (DDSH) ctia he CS khi cao, tao cho cic loai dd xuat hien rat phong phu noi sdng cho cic loli. sdng dn dinh trong dieu kien bat dn dinh ciia moi Bing 3. S6 lugng eie nhdm loii sinh vit trong eie h^ cua song nudc ta Quang CS chau Tam Pha Dam Dam Cira sdng Cac nhdm Dam Dam Ninh - Hai thd Bac Giang- Lang 0 Nha Ciru Long sinh vat Tra 6 Thi Nai Phdng bd Cau Hai Cd Loan Phu Macrophyta - 120-192 54 - 31 «30 136 104 - Phytoplanktton 185 183 357 99 85 - 185 116 278 Zooplankton - 185 38 38 38 - 64 44 36 Zoobenthos 135-500 177-183 75 45 19 36 192 172 a 200 Cdc lodi cd 280 226 171 115 38-67 133 114 93 155 Nguon: VU Trung Tang, 1994, 2009, tdng hap tie nhieu tdc gid. II. HIEN TRANG SU DUNG TAI NGUYEN VA NHUNG THACH THUC Miai thac vl NTTS 11 lpi the so sinh ndi troi nhd Ttr lau, vung CS da trd fhlnh dia bin boat ddng nhtfng dieu kien thuan lpi ciia vung. Nghien ciiU ciia manh me cua cic linh vuc kinh te. Nhin chung, viec A B. Longhurst vl D. Pauly (1987) chi ra ring, khai thac fli nguyen nhu quai de lan bien, chinh khoing 50% sd loli cl bien cd ddi sdng phu thupc vio phuc cac vfing dif mdi, khai thic RNM, dinh cl vl viing CS nhiet ddi vl khong it hon 10-15% nhu the ddi NTTS, khai khoing thudng chay theo lpi ich rieng vdi vung can nhiet ddi. Mdi quan he nay tiiy thupc cua cic nganh. Ttr dd, din den tinh trang, lpi ich cua vio tiing loli, timg giai doan phat trien khac nhau nganh nly chdng lai lpi ich cua nglnh khic, lpi ich ciia ddi sdng. O cic CS on ddi, nhu CS thupc ddng trudc mit mau thuin vdi lpi ich lau dii. Kem theo dd bing Louisiana, cd den 35-72% cic loli vl tren 90% sd 11 sir quIn ly non kem, mang tinh don nglnh, khong lupng cl the da sti dung CS nhu "vudn uom" cua phu hpp vdi clu tnic phtic tap, nhtmg rat thdng nhat chung. cua cic he sinh thii CS, dua den viec buy hoai va su Blaber S. J. M. (1980) cdn khang dinh, dai bp dting lang phi tai nguyen. Nhieu dien tich RNM bi ddn phan ca CS nhiet ddi va can nhiet doi khong mang ha, nhieu dien tich NTTS do nang suit suy giam hi bd "ban chat ctia song" ml la nhdm dac tnmg cua ngu hoang; bai de, noi kiem an cua cac loli dpng vat bien gidi vung bien nong, ntrde due vdi dd mudi rIt bien bi khuly dao, htty hoai vl 6 nhi§m, v.v do dd, sir phit ddng. Nhat 11 d cic bien phia Nam va Dong nam A, trien kinh te-xa hpi cua vung trd nen kem ben vifng. fay Phi vl phia bic My La tinh, noi nhan lupng nudc Tuy fli nguyen cua vung CS da dang, song khong Id tii nhtfng he thdng song ldn nhu: An HI, DDSH 11 dang then chdt, mang tinh ddn bay cho su song Gang (An Dp), Brakmaputi-a (Bangladesh), phit trien KT-XH cua cic huyen ven bien. Song nhat Mekong (Dong Duong), Congo (tay Phi), Amazon thiet viec khai thic vl su dung cic dang tai nguyen (Brasil) Do dd, trong sd 142 loli cl nghien ciiu d chi dupc dtmg a mtic tdi tm ml khong dupc vupt qua Nam Phi (Whitfield, 1994), cd tdi 71% sd loai la nhung gidi ban chiu dung cua chung. dai dien hoac holn toln hay mdt phan ddi sdng phu thupc vio vung CS, ti-ong dd, cl CS chiem 28% vl cl NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009
5. KHOA HOC CONG NGHE bien rpng mudi 43%, sd cdn lai 11 nhirng loli ca bien vang lai (21%), mpt sd loai la ca nudc ngpt rdng mudi hep mudi, xuat hien vdi sd lupng if nhu nhiing khach (5%) vl nhiing loli di cu qua vung CS ''^°^~ Mugil cephalus Scomberoides lysan Cu'a s6ng& ven bd' S: <35%«, nuffc trong hay due Dinhdiro'ng.^— 10-20nim Au triing song noi i Ca con Dc trirng i 1 Ck trirone th^nh • Di cu- sinh san Di chuven vio viing nu'6'c Hinh 2. Ddi s6ng cua eie loii ci phu thudc vio cua sdng (Blaber, 2000) VIo thdi gian ngap trieu, frong cac CS cd the gap bien. Ddi tupng khai thic chinh dua vao cic loai ca con non ciia nhieu loli ca them luc dia vio kiem an CS vl cl bien rpng vl hep mudi xam nhap vao cung vl trinh ke thtt thudc cic gidng: Caranx, Terapon, vdi tap doin cac loli ddng vat than mem, gilp xac ml Lutjanus, Drepane, Johnius, Plectorhynchus, ndi troi nhat 11 cic dac san nhu rong cau, tom he, Platicephlus, Polynemus, Epinephelus, Siganus, cua, ghe, sd, hau, ngao, vang, dc huong, vem xanh, Leiognathus, Gerres, Sciaena, Argyrosomus, tu hii, sa siing, v.v Cudng dd khai thac ngly mot Cynoglossus, v.v cung vdi giap xic (torn, cua), ddng cao, ngu cu cd dp chpn Ipc thap, lai sir dung phd bien vat than men (hau, sd, trai, dc), giun bien, da gai vl chat nd, xyanua vl kich dien trong khai thac. Do dd, au triing ctia chung (Vu Trung Tang vl Phan trong vai ba thap ki gin day, cong suit flu thuyen Nguyen Hdng, 1999). fang nhanh, nhtmg san lupng khai thic tang cham, chat lupng sin phim thu dupc giam do ti le con non Ngupc lai, nhieu loli giap xic vl mot sd ca (ca vl cl the chua dat kich thudc khai thic chiem 60-80% ddi, mang sifa) sdng d CS, khi thanh thuc lai ra vitng (Nguyen Long, 2005), nang suit khai thic lien tuc bien sau, xa bd de giao vT vl de tning. Tning phit giam, tii 1,15 tan/cv vao nam 1982 xudng cdn 0,35 trien den giai dpan hau au trung trd ve CS vl RNM tan/cv vio nam 2002 (hinh 3). Khai thic qui mtic (hinh 2). Nhu vay, vitng CS trd fhlnh "kho" ltm gift nhu the da xult hien ngay tft nhting nam dau ciia ngudn gien phong phu cho bien. thap ki 80 the ki trudc. Do dd, vio nhting nam gin day, san lupng dinh bat cua nghe bien hing nam giam xudng cdn 30-40% so vdi trudc nhiing nam 1990 (NguySn Xuan Ly vl nnk., 2005; Dd Van Khuong vl NguySn Chu Hdi, 2005). Di doi vdi khai thac, NTTS, mot trong 2 chan cua nghe ca, timg ddng gdp ldn cho nen kinh te qudc dan, dua nudc ta fro fhlnh mdt trong 10 nudc xult khau 1990 1991 1992 1993 1994 1995 1 1997 1998 1999 2000 2001 2002 thiiy san ldn nhlt the gidi. Tuy nhien gid day NTTS ^M s^n lOdng khai thac (tan) -nang suat khai thac (tan/cv) cung da gay ra nhiing hau qua sinh thii nang ne: thu Hinh 3. Mdi quan he giifa san lupng va nang suit hep vl hiiy hoai nhieu dien tich RNM. Dac biet viec khai thac hai san trong hon 10 nam qua tren vung md rdng dien tich NTTS da gay Ip luc ldn len stic bien nUdc ta (Bo Thuy san, 2003) ganh chiu cua bd bien bdi nan 6 nhiim, a nhieu noi da Nghe cl cua nudc ta hon nua the ki qua tap vupt qui kha nang ddng hda cua moi trudng. Day 11 trung chu yeu d vung CS, ta quen gpi la "nghe cl dieu cung rat cin dupc canh bio. long", noi sinh san vl kiem an cua cle loli sinh vat NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009
6. KHOA HOC CONG NGHE III. DINH HUONG KHAI THAC VA SU DUNG TAI NGUYEN PHUC Bdo ton cdc he sinh thdi ddc thu & vung CS ven VU CHO PHAT TRIEN BEN VUNG bien, trudc hit duy ti-i hien trang RNM, ddng thdi - Cac dang tii nguyen (TN) vung CS 11 kit qua ti-dng lai rung tren dien tich hoang hda sau khi chat cua mdi tuong tic song-bien, chung gdn bo chdt che rung, nuoi tom khong thinh, di doi vdi viec ngan v&i nhau trong mot cdu true thdng nhdt. Do dd, de chan cd hieu qui nan pha ning de dua dien tich rimg khai thic cd hieu qua, trudc het can thiet lap quy phdng hp vl RNM ven biin tdi thiiu len 60-70% cua hoach tdng the cho khai thdc tdng hap cdc dang TN mtic trudc chien tranh. cua d&i bien ven b& (coastal zone). Trong dd, lay khai Nhanh chdng lap cic di In khi thi de dua cic thdc vd NTTS la don bdy cho su phit trien KT-XH khu bao tdn biin dupc du kiin vao boat ddng, ddng tren co sd dinh gia dieu kien tu nhien, thuc trang cic thdi xic dinh cic khu vuc vl thdi gian dm khai thic dang TN, trudc bet 11 dat vl phuong thtic sti dung (tam thdi hay vinh viin). Nghiem elm tuyet ddi viec dif, xu the bien ddng cua chung dudi tic ddng ctia str dung cic phuong tien khai thac hiiy diet (thudc cic nhan td tu nhien vl boat ddng cua con ngudi. Tu' nd, xyanua, kich dien). Khuyin khich cac xi nghiep, dd xay dung cic quy hoach cho cic fhlnh phin kinh nhan dan san xuat ngudn gidng thuy san, tha ra biin te bien va cic dia phuong ven bien. nhlm fli tao ngudn lpi biin. Vung CS dang trong qud trinh phdt trien tien Trong quan li tii nguyen ciia •voing CS ven bien, hoa, rIt nhay cam vl 11 dia bin tdn tai ciia nhieu he cin chuyin ttr phuong thtic quan li don nganh sang sinh thai cd siic sin xuat cao. Do dd, boat ddng khai da nglnh, quan li tdng hpp, phu hpp vdi bin chat vdn thic fli nguyen khong duac cdn tra den chieu hu&ng cd ctia cic dang fli nguyen tdn tai thdng nhat ciia nd phdt trien cua b& bien. Vi nhu, quai de lan bien khi tuong tu nhu ddi vdi mpt don vi lanh thd hay mdt he ket clu ctia dIt chua dn dinh, chat phi RNM, chuyen sinh thai bat ki. dIt ltia "liet" vio loai nang suit thap da tfmg tdn cong - Nang cao nhan thtic ctta nhirng nhi quan li va kiem dupc trong qua trinh "thau chua, nia man" mdi cdng ddng dan cu vi luat phap chinh sIch (Luat Bao cd dupc sang NTTS nudc lp da xly ra d nhieu vfing ve Moi trudng, Luat Thuy san, Luat DDSH ), ddng ven bien, nhlt 11 d ria cle chau thd. thdi tqo hdnh lang phdp li ddm bdo cho cdc cong dong Ve dinh ca, td chuc Iqi nghe khai thdc tren co sd co ddn cu quyen duac tham gia qudn li tdi nguyen, bdo ve clu lai luc lupng dinh ca (ngu dan, ngu cu phuong tien moi truang, giit vitng an ninh vd chii quyen bien ddo. di bien va ngu trudng) vdi muc tieu chien lupc dua ddn Tdm lai, TN vl MT ndi chung hay d vung CS ndi nghe cd thodt khdi viing long ra viing nu&c sdu xa b&, di rieng, chd dua, noi tdn tai vl phit triin cua cic cdng doi vdi viec md mang nglnh nghe, tao sinh ke cho ddng din cu ngheo ven biin, ddi hdi con ngudi phai nhting ngu dan khong du nang luc tham gia dinh ca xa thay ddi cl vi nhan thtic vl hinh dpng di duy tri va bd nhlm nit ngln khoang cich giau-ngheo trong cac bao ve chung dn dinh cho su phit trien bin vung. cpng ddng dan cu ven bien. TAI UEU THAM KHAO Ve NTTS, ke ca nuoi long be tren bien vl frong (1) Nguyin Manh Hung, 2009. Ung dung cong cic eo vinh hudng den nuoi than thien vdi moi nghe GIS & vien thdm trong nghien cm xdy dung cdc trudng : i) Trudc bet phai phu hpp vdi stic ginh chiu phuang dn quy hoach, phdt trien NTTS vung dong cua bd bien, tranh vupt qui gidi ban de din den su bdng song Cm Long. Lukn kn Tien sy, Vien Sinh hpc do vo cua nghe nudi do bien khong dii siic ddng hda Nhiet ddi, TP Hd Chi Minh. cic chat thai vl bi 6 nhiim, ii) Chuyen toln bd dien tich nuoi quang canh truyin thdng vl mpt phan nuoi (2) Dd Van Khuong va Nguyin Chu Hdi, 2005. quing canh cii tien sang nuoi bin tham canh. Nuoi Bdo ve moi tru&ng vd nguon lai thiiy sdn: Nhimg thim canh cin dupc lua chpn d mtic dd nhlt dinh, iii) thdnh tmm thdch thuc, dinh hu&ng vd cdc gidi phdp. Md rdng cic ddi tupng nuoi (cic loli rong bien, tom, Trong "Bao ve moi trudng vl ngudn lpi thuy san". cl, cua ghe, than mim ) trong cic dieu kien sinh Nhi xuat bin Nong nghiep, HI Ndi, ti-.21-40 . thii xac dinh vl iv) Md rdng cac hinh thiic nuoi: (3)Lemanton, R. C. J. & Potter, L C.,1987. Nudi chuyen, nuoi xen canh (torn, lua), nuoi kit hpp Contribution of estuaries to commercial fisheries in (rong cau-tom, rimg-tom, lua-tom, mudi-cl bdng temperate Western Australia and the concept of keo ). estuarine dependance. Estuaries 10, 28-35. 8 NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009
7. KHOA HOC CONG NGHE (4) Nguyin Long, 2005. Dieu tra ca bdn nguon (9) Vu Trung Tang, 2009. Sinh thdi hoc cdc he lai hdi sdn vd dieu kien moi tru&ng cdc vting trong wa soiz^ FJef Afem. Nhlxuatban GD, Ha Npi. diem phuc vu muc tieu phdt trien Idu ben ngdnh lidi (10) Vu Trung Tang & Phan Nguyen Hong, sdn viing gdn b& bien nu&c ta. Giai doan II: Miin 1999. The role of mangroves to biodiversity and marine Trung vl Nam bp. Vien Nghien ciht Hai san. resources. Proceeding of the National Workshop (5) Longhurst A. R. & Pauly D., 1987. Ecology of "Sustiiinable and economically efficient utilization of Tropical Ocean. Academic Press, Sandiego. natural resouces in mangrove ecosystem". (6) Nguyen Xuan Ly, NguySn Chu H6i va nnk., 2005. CRES,VNU-ACTMANG, JAPAN, Nha Trang City, Tong quan ve chien litac bdo ve moi triC&ng nganli tlu'iy sdn Nov. 1-3 1998, Hanoi, 9-15. de'n ndm 2020. Trong "Bao ve moi tnrong va ngudn lpi thuy (n) Blaber, S. J. M., 2000. Tropical Estuarine san" Nha xuai ban NN, Ha Npi, tr. 41-52. ^.^^^^. ^^^^^^^^ Exploitation and Conservation. (7)D5DinhSam, Nguyin Ngpc Binh, Ngo Dinh (12) Fish and Aquatic Resources Series 7. Que, Vu Tin Phuong, 2005. Tdng quan ritng ngap man Blackwwell Science. Viet Nam Nha xuat ban Nong nghiep, HI Npi, (^3) Whitfield, A K, 1994. Fish species diversity in {S)NuTrungTdng,l99L Cdc he sinh thdi cita song Southern African estuarine systems: an evolutinary Viet Nam. Nhi xult bin Khoa hpc Ky thuat, HI Npi. perpective. Environmental Biology of Fishes, 40,37- 48. ESTUARY ECOSYSTEMS: FUNDAMENTAL CHARACTERISTICS, RESOURCES AND ORIENTATIONS FOR SUSTAINABLE DEVELOPMENT Vu Trung Tang Summary The paper presents characterized -water body of coastal zone of the tropics: Estuary systems in •which there are special ecosystems (seagrasses, mangroves ) with marine-originated eurytbermal and euryhaline flora and fauna. They have created importantiy natural resources for socio-economical development of coastal zone communities. Dominated potentials of estuary systems, especially at delta estuaries, are new land enlarging day by day towards the sea by silt deposition process from river systems and land productions, biological resources as well as other potentials for development of maritime traffic and ecotourism. More a half of the past century thousand and thousand hectas of new land of delta estuaries has been conquered by contructing marine dyke systems. Fisheries, firstiy fishing and brackish aquaculture, have contributed their important part in GDP. On contrary, above-mentioned activities have brought about seriously ecological consequences: imbalance of sea beach profile and land waste, caused by inconsederate conquest of new land, bioresources decrease, appeared from overexploitation, narrowing and destroying mangrove forests and marine environment pollution, happened by uncontroled aquaculture as well as other activities. Facing up to these situation, the paper point out some principles and solutions orienting for exploitation, utilization and management of estuaries resources for sustainable development. Keywords: Estuary ecosystem, sustainable development. Ngudi phin hitn: PGS. TS. Nguyin Xuin Ly NONG NGHIEP VA PHAT TRIEN NONG THON - SO 10 - THANG 10/2009