Los efectos de la agriculturización del humedal pampeano sobre la eutrofización de sus lagunas

The effects of the Pampas wetlands agriculturization on shallow lakes eutrophication

R. Quirós, M. B. Boveri, C.A. Petracchi, A.M. Rennella, J.J. Rosso, A. Sosnovsky y H. T. von Bernard

Area de Sistemas de Producción AcuáticaFacultad de Agronomía, Universidad de Buenos Aires

© 2005 Rolando Quirós

200m

200m

200m

63 60 57

63 60 57

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36 0.25 0.36

0.23

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the Pampas

• Central

• Flooding

factors that determine the main characteristics of thepampean wetlands

• geomorphology of the plains

• climate

• climate variability

• long-term variability

• short-term variability

• seasonal variability

short-term climate variability in the plains

Salado river discharge

020406080

100120140160180200

Q (m

3/se

c)

noviembre 2001

ciclo sequía – inundación característico del humedal pampeano“ inundación” en la sequía y “sequía” en la inundación

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verano invierno verano invierno verano invierno

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uctiv

idad

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ctric

a (m

S/cm

, 25

o C)

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descarga del río Salado (m3/seg)

sequía

inundación

sequía

inundación

sequía

inundación

sequía

1999 2000 2001

seasonal variability in very shallow lake salinity is includedRosso and Rennella, unpublished data

agroecosistemaspampeanos

humedal pampeano

insumos agropecuarios

radiación solar

producción agropecuaria

radiación degradada

degradación del humedal

diS = [∑i (µiI - µi

II) deniI + ∑i ∑r (Ai

I dξrI + Ai

II dξrII)] / T0 ≥ 0

“agriculturización” e inevitable degradación del humedal pampeano

primordial grasslands

an hypothetical landscape for primordial pampean wetlands

current grasslands (1)

fotos: INTA

current grasslands (2)

from Guerschman et al., 2001

“more agriculturization”

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1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001

year

fert

ilize

rs u

se (k

g 10

-6/y

r)

K N P

fertilizers use

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60

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120

140

160

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

year

pest

icid

es (m

illio

ns k

g or

l/yr

)

herbicides insecticides fungicides other

pesticides use

environmental efforts on the pampean wetlands

• dredging, canalization and damming of water bodies

• changes in land use patterns

• increased land erosion

• agriculture (pastures, implanted pastures, annual crops, extensive livestock growing, animal feed-lots)

• unregulated urbanization with deficient or without sewage treatment works

• unregulated land-fill usually with toxic substances

environmental effects in the pampean wetlands

• changes in natural hydrological patterns

• changed morphology of water bodies

• increased inorganic sedimentation

• increased levels of non-oxidized organic matter and its metabolites

• nutrient enrichment (mainly P and N)

• contamination of surface waters and groundwater with toxic substances commonly used in modern agriculture (herbicides, insecticides, and other agro-toxic substances)

• contamination of surface waters and groundwater (?) with highly toxic substances used in industry

• huge changes in vegetal and animal biodiversity and abundance for both terrestrial and aquatic ecosystems

Central Pampas

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60

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100

1881 1914 1937 1960 1988 2002

natural pastures cultivated pastures annual crops modified from Viglizzo et al., 2001

Flooding Pampas

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60

80

100

1881 1914 1937 1960 1988 2002

natural pastures cultivated pastures annual crops modified from Viglizzo et al., 2001

Total Pampas

0

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60

80

100

1881 1914 1937 1960 1988 2002natural pastures cultivated pastures annual crops

"natural" land

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1881 1914 1937 1960 1988 2002

mill

ions

of h

ecta

res

Central Pampas Flooding Pampas Total Pampasmodified from Viglizzo et al., 2001

los lagos someros (lagunas):

componente central del humedal pampeano

10-1

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TP (mg.m-3)

Chl

(mg.

m-3

)

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10-1

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10-1 100 101 102 103

Chl (mg.m-3)

SDL

(m)

“claras” y “turbias”

a

b

lagunas “claras” y “turbias” como indicadores de la intensidad de acción antrópica sobre el humedal pampeano

"natural" land

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10

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1881 1914 1937 1960 1988 2002

mill

ions

of h

ecta

res

Central Pampas Flooding Pampas Total Pampas

lagunas “claras” lagunas “turbias”

100

101

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103

101 102 103 104

TP (mg/m3)

Chl

(mg/

m3)

37 lagunas pampeanas, “turbias” (O) y “claras” (O)

-3

-2

-1

0

1

2

3

-3 -2 -1 0 1 2 3PCA - 2

PCA

- 1

“claras”

“turbias” planctívoros

piscívoros TN:TP

MASI

nutrientesfitoplancton

“claras” y “turbias”

“claras” y “turbias”

-3

-2

-1

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-3 -2 -1 0 1 2 3

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11 1

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11

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24

23

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33 2

22

444

4

4444

PCA - 2

PCA

- 1

“claras” y “turbias”

100

101

102

103

101 102 103 104

TP (mg/m3)

Chl

(mg/

m3)

flooding pampas

central pampas

central pampas

flooding pampas

for pampean terrestrial ecosystems, dramatic changes in weighted biodiversity have been widely documented for vegetal and animal communities, therefore, only some changes in the biota of the aquatic component of the pampean wetlands will be presented here:

lake phytoplankton“clear” and “turbid” lakes

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1 2clear = 1 turbid = 2

% c

yano

bact

eria

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1 2clear = 1 turbid = 2

# cy

anob

acte

ria

lake fish changes from “clear” to “turbid” very shallow pampean lakes

water transparency = 1.50 m"clear" lakes

visual planktivores

35%

top predator16%

detritivorous17%

other24%filter feeding

planktivores0%

carp8%

"turbid" lakes

carp3%

filter feeding planktivores

1%

other17%

detritivorous20%

top predator5%

visual planktivores

54%

water transparency = 0.38 mupper Salado "turbid" lakes

visual planktivores

52%

top predator3%

detritivorous10%

other4%filter feeding

planktivores21%

carp10%

water transparency = 0.23 m

from primordial wetlands to agricultural land

past present

• natural grasslands• natural drainages

• “clear” lakes• macrophyte dominated• usually with oxic, P unsaturated

sediments• balanced vegetal and animal

communities• relatively low levels of organic

matter, more oxidative environments• nutrient levels according to drainages

on highly productive soils

• agriculture, human settlements and highly modified grasslands

• drainages medium to highly modified

• “turbid” lakes• phytoplankton dominated• hypoxic and anoxic, P saturated

sediments • simplified vegetal and animal

communities• high levels of organic matter,

reductive environments• very high nutrient levels due to

agriculture and urbanization• extended fish and avian mortalities• human health hazards

muito obrigado!

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