*3.4. Perceived Threats to Blue Carbon Ecosystems*

The residents were asked to rank the threats based on their perceptions from most (1) to least (10) damaging threats (Table 4). Almost half (48.5%) of the respondents of Busuanga have identified natural disasters (i.e., typhoons, storm surges) to be the most (1st) concerning threat to mangroves whereas conversion to fishponds is perceived by 64.9% to be the least (10th) threat. Illegal cutting of mangroves (18.6%) came second in the rank along with pollution from domestic wastes (34.7%). Other perceived anthropogenic threats to mangroves like charcoal making, increasing population, informal settlers, building coastal infrastructures, conversion to nipa and coconut plantation, and conversion to residential areas ranked fourth (34.7%), fifth (30.6%), sixth (21.4%), seventh (26.8%), eighth (35.7%),

and ninth (50.5%) places, respectively. Conversely, perceived threats in Karimunjawa are ranked differently (Table 4). For instance, 28.3% of the respondents of Karimunjawa have recognized natural disasters to be the least (10th) damaging threat to mangroves opposite to Busuanga's results. The difference is statistically significant (*p* < 0.05) based on the Mann– Whitney U test. Other significant differences on perceived threats observed in Karimunjawa include charcoal making (3rd, 21.7%), building infrastructures (third, 17.4%), conversion to fishponds (fifth, 19.6%), conversion to residential areas (sixth, 23.9%), conversion to palm tree plantation (eighth, 21.7%), and increasing population (ninth, 28.3%).


## **Table 4.** Perceived threats to blue carbon ecosystems.

Notes: <sup>a</sup> Most frequently occurring response, <sup>b</sup> measured from most (1) to least (10) damaging threats. \* difference is statistically significant at *p* < 0.05 based on the Mann–Whitney U test.

> Seagrass ecosystems are also highly vulnerable to natural and anthropogenic threats. Pollution from domestic wastes ranked first in the list of damaging threats in both study sites (Table 4). Similar to mangroves' threats, natural disasters occurring in Busuanga are also perceived by 39.8% of the sample size to be at the top list of threats whereas 28.3% of the respondents of Karimunjawa ranked it at the bottom of the list along with increasing sea surface temperature (23.9%). Moreover, mangrove planting in seagrass beds (18.4%) and building infrastructures in coastal areas (17.3%) in Busuanga tied in fourth place followed by sand mining (16.3%), unregulated gleaning (21.4%), and siltation (17.3%) all in sixth place. Beach reclamation and increasing sea surface temperature are perceived to be the least threats, occupying the 9th (33.7%) and 10th (52.0%) places, respectively. Meanwhile, in Karimunjawa, unregulated gleaning and beach reclamation are ranked significantly different (*p* < 0.05) taking the second (19.6%) and fourth (19.6) places, correspondingly.
