Efektifitas Revegetasi Mangrove Menggunakan Alat Pemecah Ombak Dari Pohon Nibung

Sebagai negara benteng terakhir penghasil oksigen, Indonesia patut berbangga sebagai negara dengan jumlah hutan yang luas—meski laju deforestasi juga mengkhawatirkan. Lebih mengejutkan lagi, berdasarkan hasil penelitian dari CIFOR, hutan mangrove Indonesia disebut menyimpan lima kali karbon lebih banyak per hektare dibandingkan dengan hutan tropis. Belum lagi dengan produksi oksigen oleh lamun dan fitoplankton. Maka perlu dilakukan kegiatan revegetasi mangrove yang efektive dan efisien.

Selain berperan sebagai penghasil oksigen, mangrove juga sangat berperan dalam menjaga biodiversitas lingkungan, yang mana secara ekologi, mangrove berperan sebagai pendukung berbagai jasa ekosistem, termasuk produksi perikanan dan siklus unsur hara. Selain itu, secara ketahanan dan keamanan negara, secara tidak langsung mangrove juga turut berperan, di mana mangrove berfungsi untuk menjaga garis pantai agar tidak terabrasi. Dengan struktur pengakaran yang unik dan khusus untuk beradaptasi dengan kandungan salinitas dan empasan gelombang, mangrove menjadi benteng utama yang menjaga agar kawasan pesisir tidak tergerus oleh gelombang.

Namun, kenyataan seringkali pahit. Berdasarkan data FAO (Organisasi Pangan Dunia, PBB) dalam tiga dekade terakhir, Indonesia sudah kehilangan 40% mangrove, yang berarti, Indonesia memiliki kecepatan kerusakan mangrove terbesar di dunia [1]. Menurut data yang dihimpun dari Biro Humas Kementerian LHK pada tahun 2015, Indonesia memiliki ekosistem mangrove terluas di dunia sebesar 3.489.140,68 Ha, dengan panjang garis pantai sebesar 95,181 km2 serta memiliki keanekaragaman hayati yang paling tinggi. Kalau diestimasikan, luas ekosistem mangrove Indonesia setara 23% ekosistem mangrove dunia yaitu dari total luas 16.530.000 Ha. Dari luas mangrove di Indonesia, diketahui seluas 1.671.140,75 Ha dalam kondisi baik, sedangkan areal sisanya seluas 1.817.999,93 Ha sisanya dalam kondisi rusak [2].

Tingginya kerusakan mangrove di beberapa daerah di Indonesia, setidaknya berhasil membuat seluruh pihak—baik pemerintah, swasta, maupun perseorangan—bahu membahu berjuang untuk menyelamatkan mangrove yang sudah telanjur rusak. Pemerintah dengan dana APBN maupun pinjaman luar negri (terbaru pemerintah berupaya untuk menanami kawasan pesisir yang terancam abrasi. Begitu juga dengan swasta maupun kelompok penyelamat lingkungan. Kendati demikian, upaya penanaman kembali atau rehabilitasi lahan mangrove yang sudah rusak, ternyata tidak semudah dengan melakukan perusakan itu sendiri. 

Kebanyakan, penanaman mangrove yang dilakukan oleh berbagai pihak menemui kegagalan. Bibit mangrove yang ditanami, tidak banyak yang bertahan hidup sampai dewasa. Logikanya, mangrove memang mampu menahan gelombang—namun tentu saja itu adalah mangrove dewasa yang merumpun dan zonasinya lengkap serta sehat. Hal itu tentu tidak akan berlaku bagi propagul alias bibit mangrove yang baru tumbuh. Tentu saja ketika menanam bibit mangrove tanpa ada penahannya akan mengakibatkan bibit tersebut hanyut terbawa gelombang. 

Untuk mengatasi hal ini, akhirnya upaya penanaman mangrove di lahan kosong, seyogyanya membutuhkan alat pemecah ombak (APO) untuk menggantikan peran mangrove dewasa sebagai penahan dan pemecah gelombang, baik itu dengan berbagai struktur solid pemecah gelombang, seperti tetrapod, batuan karang, maupun struktur lunak menggunakan hybrid engineering. 

Pemanfaatan Nibung Sebagai Pagar APO 

Nibung telah ditetapkan sebagai flora khas identitas Provinsi Riau. Pasalnya pohon ini sudah lama menyatu dengan kehidupan masyarakat Riau. Hal ini terbukti dengan adanya beberapa tempat, yakni Tanjung Nibung, Teluk Nibung, yang mengabadikan nama tumbuhan tersebut. Selain itu keterkaitan ini tampak pula dalam pantun ataupun ungkapan tradisionalnya. Pemanfaatan nibung Sebagai Pagar APO telah diterapkan di Desa Pangkalan Jambi, Kecamatan Bukit Batu, Kabupaten Bengkalis, Riau. 

Pemanfaatan nibung sebagai APO tergolong berhasil dalam mencegah abrasi Pantai di Pangkalan Jambi, sekaligus berhasil melindungi pertumbuhan Avicennia. Keberhasilan Nibung sebagai APO dikarenakan sifat kayunya yang tahan lapuk (sampai belasan tahun), kemudian tahan terhadap empasan gelombang.

Adapun spesifikasi nibung yang sudah bisa dijadikan APO adalah nibung dengan ukuran minimal 4” (empat inci) atau dengan diameter kurang lebih 14-15 cm dan keliling sekitar 47 cm. Untuk penggunaan Nibung sebagai Pagar APO batang dibung dibelah 2,sehingga untuk satu batang Nibung dengan diameter 14 cm dapat membuat APO sepanjang 28 cm. Untuk mendapatkan Pagar APO sepanjang 1 meter dibutuhkan 4 potong kayu nibung. 

Ketinggian APO yang dipasang di Pesisir Desa Pangkalan Jambi yaitu setinggi 60 cm dari permukaan lumpur, sedangkan yang tertanam didalam lumpur sepanjang 30-40 cm. Sehingga untuk membuat Pagar APO sepanjang 1 meter dibutuhkan 4 Potong Nibung dengan Panjang Potongan 1 meter. 

Tabel. Perkiraan kebutuhan Biaya untuk pembuatan APO nibung sepanjang 1 meter:

Dengan pembangunan pagar APO dari Nibung sepanjang 100 meter disepajang bibir pantai, berpotensi menanam 1000 batang bibit Avicennia yang terjamin tinggi pertumbuhannya. Namun, tetap dibutuhkan kajian ilmiah terlebih dahulu terkait pasca pemasangan pagar APO, “Seberapa lama waktu yang dibutuhkan agar subtrat lumpur media tanam terperangkap, sehingga keberhasilan tumbuh Avicennia bisa terjamin”.

Gambar . Desain APO

Sumber : Rafi Merbamas

Adaptation Strategy Indonesia

Indonesia aims to reduce the vulnerability of its economy and community to adverse impacts of climate change that are already occurring. At the same time, Indonesia intends to prepare its national and local institutions, as well as vulnerable communities, for the possible future impacts of climate change. These preparations will include measures to increase adaptive capacity through improved planning, enhance resource management, and expand coordination to deal with inter-sectoral and cross-cutting issues.

Indonesia has established the Indonesia Climate Change Sectoral Roadmap (ICCSR 2010 - 2030) ) to set its national goals, sectoral targets, milestones and priorities for actions with regards to adaptation and mitigation of climate change for all affected sectors of the economy.

To deal with and to minimize the impact of climate change, Indonesia shall concentrateon activities based on following strategies :

1. To enhance knowledge about the hazard and impacts of climate change to the ecosystem and community’s livelihood

2. To integrate the climate change issues into the national and regional development planning

3. To integrate the climate change issues in the spatial planning of the urban, rural areas and, and small islands.

4. To build the capacity of the regional governments in formulating the strategies and climate change adaptation activities as well as to recognize, support, and facilitate smart adaptation efforts made by the community.

5. To develop and use technology to support the adaptation efforts and to improve community’s sustainability in dealing with climate change impacts, especially in order to increase food sustainability and health quality.

6. To increase the application of climate information in the activities of agriculture, fishery, health, water resources management and disaster management in order to increase community’s resilience in adapting to the climate change.

7. To formulatethe policies and protection tools for the most vulnerable groups of people who are not able to anticipate and adapt to the climate change.

Next, the priority of adaptation activity in each sector is determined in the context of facing the challenge, risk and vulnerability which is unique and distinct in each sector. The priority of adaptation activity in the sector of marine and fishery, health, agriculture, water resources and climate related disaster management is elaborated as follows:

Impact Climate Change on Disaster Incidents

Threat of drought due to El Nino phenomenon is certainly (again) a supporting factor for forest fire which has been destroying million hectates of forest area. In reference to forest fire in 1997/1998 which destroyed an area of 9.7 million hectares, the aftermath of which has exacerbated the socio economic and environmental loss at national level as well as at neighboring countries. On the other hand, an incident such as flood and landslide has also increased in intensity. This is due to extreme change in rainfall pattern such that rain distribution falls out of pattern compared with previous seasons.

The climate change has increased both natural disaster and non-natural disaster risk experienced by the community. The most likely impact of climate change in Indonesia is the increased of rainfall frequency which affects infrastructure and housing damage in a way that many people lose their homes. Natural disaster such as flood accounts for 1/3 of all disasters taking place in Indonesia dan has claimed more than 50% lives and

1/3 of total economic loss due to disaster. Climate change has also been responsible for intensifying tropical storm and the increase of of high tide frequency at the sea, which in turn enlarges the risk of death.The impacts of climate change on other disasters incindents can be observed in the following table:

Table 3 Impact of Climate Change on Disaster Management

Impact Climate Change On Water Resource

The analysis result by the Geographic Information System (GIS) describes comparatively the risk of water availability reduction in Indonesia during 2010-2015 up to 2025-2030 period as effected by the climate change. The impacts include:

1. Reduced Water Availability

There are five risk levels with the highest level of water availability reduction is found in the region of Java-Bali, particularly in several limited areas in the northern and southern parts of West Java, central and southern part of Central Java and East Java, in the capital city of North Sumatera, West Sumatera, Bengkulu and Lampung (Sumatera); Bali, NTB (Nusa Tenggara) and South Sulawesi (Sulawesi); whereas the high risk of water availability reduction is in about 75% of Java-Bali region; a minor parts in the northern, western and southern region of Sumatera; some parts of Lombok Island (Nusa Tenggara), and South Sulawesi (Sulawesi).

2. Flood

There are five levels of flood risk and flood distribution, with the highest flood risk is found very limitedly along the big rivers, particularly at the downstream in Java, eastern part of Sumatera; West, South, and East Borneo; East Sulawesi, and South Papua, whereas the high flood risk is found in the same regions of highest flood risk, only with greater area size.

3. Drought

The highest drought risk is found in general in the limited region in the central part of Java; northern part of Sumatera, and minor part in Nusa Tenggara, whereas the high drought risk is found in the greater area size in the central part of Java, Sumatera, and Nusa Tenggara;

4. Landslide

The highest landslide risk is generally found in the central and southern parts of Java-Bali, central and western parts of Sumatera, the most parts of Nusa Tenggara, and Sulawesi, and also central part of Papua, whereas the high landslide risk is found along the highest landslide risk areas as mentioned above with narrower areas.

5. Sea water intrusion

The potential impact of sea water intrusion in line with the danger and vulnerability of sea water intrusion is limited to several coastal areas, particularly in the regions of Java-Bali (Jakarta, Semarang, Denpasar) and Sumatera (Palembang and Padang). The risk of sea water intrusion is prompted by the increasingly shallow sea water surface - sea water interface at the coastal areas as well as related vulnerability including population density, land usage, water requirement and deep water drilling. Sea water intrusion causes reduction on water supply due to water quality deterioration and also land or building foundation damage.

Impact Climate Change on Agriculture Indonesia

The climate change which induces rainfall pattern change, temperature rise, and sea level rise has effects on the quantity and quality of agriculture yields, especially food crops. Farmers are finding it more difficult nowadays to determine the suitable types of plants and planting calendar due to unpredictable climate. In various areas in Indonesia, drought and flood have destroyed food crop harvests. There were many rice paddy fields destroyed or simply failed to produce due to long dry season or flood. The main impacts of climate change on agricultural areas in Indonesia are the degradation of land and water resources as well as damage on infrastructure (irragation).

For example, rainfall pattern change and extreme climate cause rice paddy fields in several regions/areas to experience drought when other areas are damaged by flood. The result of all that is the potential increase of diminishing yields from 2.4-5 percent to become more than 10 percent (R&D Ministry of Agriculture, 2008) During period of 1991 to 2006, the area of rice paddy fields suffered from drought was around 28,580 to 867,930 hectares per year and damaged area was about 4,614 to 192,331 hectares (Directorate of Plant Protection, 2007). A more widespread drought was experienced during El Nino years (Graph1)

Graph 1 the size of Rice Paddy Fields Affected by Drought and Flood in Indonesia within the period of 1991-2006

The growing threat of flood on rice paddy fields is responsible for the declining harvest area and reducing rice paddy production. Nationally, the flood vulnerability level per district in the entire territory of Indonesia can be observed from Graph 1. In Java, the size of rice paddy fields which is prone to flood/inundation reaches 1,084,217 hectares, and the extremely prone ones are 162,622 hectares, whereas in Sumatera there are 267,278 hectares, 124,465 hectares out of which are found in South Sumatera and 50.606 hectares are found in Jambi. Based on the report of the Directorate of Food Crop Protection (2007), the size of area affected by flood within 16 years period (1991-2006) fluctuated with average size of damaged area of 31,977-32,826 hectares and 5,707-138,227 hectares failed to produce.

More so towards year 2050, without any national effort to adapt to climate change, it is estimated that the strategic food crop yield will decline by 20.3-27.1% for rice paddy, 13.6% for corn, 12.4% for soybean, and 7.6% for sugar cane compared to the condition in 2006. The potential decline for the rice paddy yield is related to the declining of rice paddy field for the size of 113,003-146,473 hectares in Java, 1,314-1,345 hectares in North Sumatera, and 13,672-17,069 hectares in Sulawesi (Handoko et al. 2008). The extent of loss due to sea level rise against the rice paddy field shrinkage in the form of rice paddy production in 2050 is

Table 2 The Impact of Sea Level Rise Against the Decrease of Rice Paddy Field Coverage and Paddy/Rice Production until Year 2050