Wetlands and Global Climate Change:

The Role of Wetland Restoration

In a Changing World

Kevin L. Erwin Consulting Ecologist, Inc.

Florida Gulf Coast University

Department of Marine & Ecological Sciences

2077 Bayside Parkway

Ft. Myers, Florida 33901 USA

www.environment.com

23rd Annual Southwest Florida Water Resources Conference

Florida Gulf Coast University

January 31st, 2014

CRITICAL CONDITIONS WITHIN THE CASAMANCE CATCHMENT OF

SENEGAL: AN OPPORTUNITY FOR RESTORATION OF WETLANDS

AND LIVELIHOODS

A LOOK INTO THE FUTURE OF POORLY MANAGED ECOSYSTEMS

AFFECTED BY CLIMATE CHANGE

Three of the world’s greatest challenges over the coming decades will be

biodiversity loss,climate change, and water shortages. Biodiversity loss will

lead to the erosion of ecosystem services and will increase vulnerability to

the impacts of climate change.

The Millennium Ecosystem Assessment (2005) is an

international synthesis by over 1000 of the world's leading

biological scientists that analyzes the state of the Earth’s

ecosystems and provides summaries and guidelines for

decision-makers. It concludes that human activity is having

a significant and escalating impact on the biodiversity of

world ecosystems, reducing both their resilience and

biocapacity. The report refers to natural systems as

humanity's "life-support system", providing essential

"ecosystem services". The assessment measures 24

ecosystem services concluding that only four have shown

improvement over the last 50 years, fifteen are in serious

decline, and five are in a stable state overall, but under

threat in some parts of the world.

9/12 10/12

China

China and Africa are the areas in which we are

now working on water resource issues and the

livelihoods of those people who directly depend

on the ecosystem services provided by their

wetlands. It’s a life and death situation, unlike

most of us in our society that can subsidize the

loss of our natural capital.

Rainfall has diminished

over the past three

decades from

approximately 1000mm

annually to the current

levels of approximately

300 to 500mm with long

dry periods between

heavy rains that cause

many problems related to

erosion and crop

destruction. It’s not just

the amount of rain that is

critical but the timing of the

rainfall.

Senegal is a low-income,

food-deficit country of 14

million people.

Approximately 80 percent

of the population works in

agriculture, depending on

exhausted soils and

rainfall that fluctuates

from year to year.

On the edge of the Sahel they are

“living” climate change. This has led

to food shortages and poverty such

that 26 percent of the population is

undernourished and chronic

malnutrition levels are particularly high

among children under five.

This is where our late season north

Atlantic hurricanes are typically born which

is a topic for another time.

The global mangrove area presently does not

exceed 180,000 sq. km (Myers and Kent, 2005),

a relatively small area extent for a natural

ecosystem. Their scattered distribution along

the intertidal zones of tropical and subtropical

coastlines is primarily characterized by tidal

regimes that create unique forest habitats.

Globally, mangroves are known to consist of

approximately 70 species; however, the species

distribution varies from more than 30 species

along the richest coasts of Australia and

southeast Asia, to only one species recorded

today in most of the arid Middle East.

The world has lost around 3.6 million hectares

of mangroves since 1980, equivalent to a 20

percent loss of total mangrove area, down to

15.2 million hectares in 2005 (FAO, 2007).

� Protecting and restoring vast amounts of mangrove

habitat is important to mitigate some climate change

impacts such as attenuating increased incidences of

floods and catastrophic tropical cyclones.

� Establishing new zones of mangrove habitat where there

is no conflict with human development so that as sea

level rises and mangroves die-back, they are

replenishing themselves at the landward extent of the

intertidal zone.

� If this is not done, in the future, the substantial areas of

mangrove forest will be gone and with it the huge engine

that provides the carbon base of the tropical marine

ecosystem (Erwin, 2008).

Deforestation of mangrove communities is one

of the major reasons for the decline in coastal

fisheries of many tropical and subtropical

countries. Although mangroves in the tropics

can regenerate themselves or be restored using

low-technology propagule planting, mangroves

in regions having limited access to fresh water

can seldom regenerate, and if they do, it

happens very slowly.

Estuarine hydraulics is dominated by the tide,

the fresh water discharge and evaporation.

Normally the net water flux in an estuary is

positive in downstream direction. However if

the evaporation is high compared to the fresh

water discharge, the net water flux (saline) is

upstream.

This process is typical for an inverse estuary.

This is the case for the Casamance estuary.

The watershed of the Casamance estuary is

approximately 23,834 sq.km in size and very flat.

March 2003 Landsat

Image of Dialoulou

If the annual fresh water discharge is not enough to

flush the estuary, a yearly net accumulation of salt

occurs. This is the case for the Casamance. After a

number of consecutive years of salt accumulation the

estuary has turned into a hypersaline estuary.

Salinty PPT Name Watershed Coordinates

3 DIANA MILARI Casamance N12 50.972' W15 15.101'

10 CHINESE DAM Casamance 12°40'1.23"N 16°20'33.57"W

37 ABENE Casamance N12 59.822' W16 43.725'

43 DIAKENE PROPAGULE COLLECTION SITE Casamance N12 27.502' W16 38.36'

45 DJIRNDA SEL 2008 PLANTING SITE Saloum N13 57.978' W16 37.385'

52 KAMEBEUL BOLON Casamance N12 26.966' W16 27.499'

52 TOBOR #206 Casamance 12°38'42.73"N 16°16'0.14"W

54 SEDHIOV Casamance N12 42.486' W15 33.023

55 DIAO SIMACOUNDA PLANTING SITE Casamance N12 40.569' W15 59.235

56 NIAMDIAROS Saloum N14 08.475' W16 28.325'

58 TOBOR #208 Casamance N12 37.073' W16 16.779'

58 AFFINIAM DAM Casamance 12°39'59.53"N 16°20'30.67"W

60 FIMELA (NON-OCEANIUM) Saloum N14 07.934' W16 39.418'

62 BASIS PLANTING SITE (NON-OCEANIUM) Saloum 14° 3'58.01"N 16°26'4.52"W

63 FIAKO 2008 PLANTING SITE Saloum N14 11.506' W16 27.182'

68 BAILA PLANTING SITE Casamance N12 53.895' W16 21.541'

68 DIOLOULOU 2008 PLANTING SITE Casamance N13 02.484' W16 35.767'

68 YIMBEN PLANTING SITE Casamance N12 58.534' W16 41.504'

70 NIAMBALANG Casamance N12 26.996' W16 29.881'

70 O.B. BRIDGE Casamance N12 26.966' W16 27.499'

70 TOBOR #206 Casamance 12°38'44.81"N 16°16'6.34"W

72 PONT BAFICA 2008 PLANTING SITE Casamance N12 28.490' W16 23.420'

76 DIANA 2008 PLANTING SITE Casamance N12 58.510' W16 42.312'

77BASIS PLANTING SITE (NON-OCEANIUM)

Saloum 14° 4'2.10"N 16°26'3.18"W

When a typical estuary morphs into a hypersaline

estuary it causes significant impacts to the flora and

fauna, because the endemic plant species, including

mangroves, cannot adjust to the high salt

concentrations and die, leaving extensive barren mud

flats behind.

Since 1983 several 9 anti-salt dams have been

constructed in the tributaries of the Casamance

estuary to reclaim salty upstream grounds and

use the land for rice cultivation. These

structures have blocked sediment transport and

nutrients being supplied downstream impacting

both mangroves and fisheries creating

significant impacts to fisheries and the

livelihoods of those dependent on this resource.

Currently, many of these rice paddies and

upland farms have been abandoned, possibly

due to a reduction in rainfall and an increase in

salinity of ground and surface waters.

Fisheries and oyster collection, important protein rich

food resources that once thrived here have been

destroyed by the hypersaline conditions and the mass

decline of mangrove forests which has given way to

extensive tannes.

The most vulnerable people are typically

those whose livelihoods directly depend

on nature and on the ecosystem services

that their wetlands provide.

A local fish drying cooperative near the mouth of the Casamance River

Here it’s a life and death situation, unlike most of our

society where we can subsidize the loss of our natural

capital.......the question is for how long?