I will add a few more reasons to what has been said by Gregor.

Development of new ports in the 3rd world countries has lead to destruction of these trees. With these anthropogenic activities comes in the deposition of oil used by these marine vessels, it annihilates the growing plantling. The local govt. gives freedom to those camel owners to graze on the mangroves during times of draught in their areas.

I completely agree with these comments. I would like to add hydrological changes in watersheds. Water river is largely used in irrigation (large quantity of this water is derived to the underground water), and sometimes water river is trespassed from one watershed to another and of course water regimen in the coast y largely affected, producing siltation and sedimentation and the death of mangrove.

i thank you all for your help

Dear Mehreen,

The question you raised is important. I think other respondents have given you their options and I agree with that. I believe the threats are: Inundation of mangroves due to increasing sea level and deforestation of mangroves are the major threats.

 ‍I think see level rise, cyclone, storm surges and increasing degree of salinity severely affected the natural and manmade mangrove forests. In some places less inundation due to rising up forest floor is another threat to the mangrove forest.

I agree with the above answers and would add the following comments.  In tropical America (including the Caribbean), the conversion of mangroves to shrimp ponds is the most prominent cause of the loss of mangroves.  Often unmentioned are the critically important environmental services provided by mangroves such as buffering against tropical cyclones, hurricanes, and lesser storms, and serving as a nursery for marine biota.

In Fiji major threats are climate change resulting in increase sea level, development along coasts as tourism is Fiji's major foreign income earner and the shift of population from rural to urban areas where a lot of squatter settlements have developed in mangrove areas and use of mangrove as firewood.

Hello Mehreen

I pass some links to current studies on degradation of mangroves. These address causes of climate change and direct interventions of people, in some contexts. Regard. 

https://www.researchgate.net/publication/262151388_Using_expert_knowledge_and_modeling_to_define_mangrove_composition_functioning_and_threats_and_estimate_time_frame_for_recovery

http://link.springer.com/article/10.1007/s40641-015-0002-x#/page-1

https://www.researchgate.net/publication/275271024_Applying_Climate_Compatible_Development_and_Economic_Valuation_to_Coastal_Management_A_Case_Study_of_Kenya%27s_Mangrove_Forests

https://www.researchgate.net/publication/257657892_Impacts_of_shrimp_farming_on_the_coastal_environment_of_Bangladesh_and_approach_for_management

https://www.researchgate.net/publication/281586330_Mangrove_response_to_sea_level_changes_and_monsoon_variability

https://www.researchgate.net/publication/266260796_The_importance_of_mangroves_to_people_a_call_to_action

https://www.researchgate.net/publication/285592581_Behavioral_Change_Due_to_Climate_Change_Effects_Accelerate_Tiger_Human_Conflicts_A_Study_on_Sundarbans_Mangrove_Forests_Bangladesh?ev=srch_pub&_sg=ISykKC9O0mQEfGUmXSNWY_EvE0QnrTZ3kpZfCXlLMS24OS83mEub0aGhbczz6skj.36DFfEibi9S6TwMfovxREPOfXABETcecggHiI6Lp6n1SOFjCm9tPcStkabzyI4QR.TtjrPba_l42PSLorRD3EHVsKijVyUBOZTDk-mBvP7-O5m2xTCYixMhfFWdmf7tIv

Article Using expert knowledge and modeling to define mangrove compo...

Article Applying Climate Compatible Development and Economic Valuati...

Article Impacts of shrimp farming on the coastal environment of Bang...

Conference Paper Mangrove response to sea level changes and monsoon variability

Technical Report The importance of mangroves to people: a call to action.

Article Behavioral Change Due to Climate Change Effects Accelerate T...

i thank u all, it was really of great help

Mehreen,

There are several threats to the mangrove ecosystem though they may vary from region to region. In Nigeria for instance, the major threats to the mangrove forest include crude oil pollution, logging, firewood gathering, fish farming, building of settlements for oil workers, land reclamation for infrastructure, and the invasion of  nypa palm.

I send three papers. 

Regards

http://190.11.224.74:8080/jspui/bitstream/123456789/2016/1/2008%20Threats%20to%20mangroves%20from%20climate%20change.pdf 

http://www.ingentaconnect.com/content/umrsmas/bullmar/2013/00000089/00000002/art00013?crawler=true&mimetype=application/pdf

https://www.researchgate.net/profile/Grillo_Oscar/publication/235898444_Ecosystems_biodiversity/links/0912f513efcbcf354a000000.pdf#page=282

Book Ecosystems biodiversity

I think , biggest threat to mangrove forest is  our inability to gauge the intensity of climate change and remediative measures to address the changes inflicted . the huge loss of plant  diversity ( Could be some useful microbial diversity as well , who knows) is the singled out example in this regard.   

I am working on mangrove ecosystems of Gautami Godavari estuary since 1985, I have been noticed a lot of change in the canopy and abundance of the mangoves. This is mainly due to the anthropogenic acitivities.Human settelements and establishments play a important role in depletion of the mangrove ecosystem. Further little action was initiated to restoration and regeneration of these ecosystems

I think that world wide the biggest threats to mangrove forests are urban industrial expansion, brackish water aquaculture, tourism and squatter settlements.

In addition to all of the above, cutting poles for construction of houses is forming a major threat to mangroves.

The major threats to mangrove forests include population explosion, conversion to aquaculture ponds, clear-felling for timber, charcoal and wood chip production for industrial and urban development.

I can see that Mehreen's question has generated a lot answers regarding the threats to the mangrove ecosystem in different parts of the world. Considering the importance of the mangrove ecosystem, the need for its regeneration and restoration cannot be overemphasized. It will be nice if we can share some strategies, techniques and methods that have been adopted to tackle the menace of mangrove deforestation and degradation in our various countries and regions. Information on innovative approaches to regeneration and restoration will equally be useful.

Climate change is a new emerging threat to mangrove forests.

Article The Impact of Climate Change on Mangrove Forests

Article Impacts of climate change on mangrove ecosystems: a region b...

Article A Review of Climate Change Impacts on Mangrove Ecosystems

Article Threats to mangroves from climate change and adaptation options

From the various contributions so far, the major threats to the mangrove forests can be said to include pollution including oil pollution, climate change, high impact logging and unsustainable exploitation of other resources derived from the mangrove forests, firewood gathering, building of settlements for oil workers, land reclamation for various infrastructure, invasive alien species, charcoal production, fish/shrimp farming, animal fodder gathering, urban/industrial expansion and population explosion.

A lot of factors indeed. However, considering the important roles the mangrove ecosystem plays, the need for the regeneration and restoration of degraded mangrove ecosystems across the globe cannot be overemphasized. In view of this, I will like us to take this discussion one step further by sharing approaches, methods and techniques that have been or are being employed for the regeneration and restoration of degraded mangroves in our various countries and regions. I believe that the sharing of such information will further help to conserve this important ecosystem.

Yes, I agree with Dr. Arvind.

Best regards.